# 26 Jun, 2020 22:29
Two months ago I started out on this wonderful hobby with an unmodded Canon 6D Mk II and a Star Adventurer Mount.
My first upgrade was a Canon 200mm EF f2.8 lens which I operate at f4 to give me good images over (almost) the full frame.
I am absolutely loving the adventure, but really feel the need to move on and up.
200mm on a Star Adventurer is really pushing it. Without auto guiding, I am limited to 30secs; the worm gear errors leading to 10-15% of sub-frames being rejected. [At 60secs this rises to 60secs…].
I also would like more aperture, more red response and a little more resolution. My imaging will be done primarily (exclusively) from my backyard under Bortle Class 3 skies.
As a first step - and because everyone says it is the most important item- I have ordered an EQ6 Pro - now I need to work out what to put on it. Since this will be my rig for at least the next 10-15 years, my budget is up to USD5000.
My thoughts are:
1) Sky Watcher Esprit 100mm at f6: Beautiful images, easy to use, but smaller aperture and expensive
2) Celestron RASA 8inch: Big aperture, super fast, but image quality and collimation an issue.
3) GSO 8inch Rithcey Cretian: Good image quality, relatively inexpensive but the slowest f ratio.
1) Canon RA: easy to use, expensive not cooled
2) ZWO 533MC Pro: low noise, no amp glow, small(ish) chip [The 294MC also looks good but I am worried about amp glow]
3) ZWO 1600MM: low noise, big chip, but serious investment in time/energy that come from filter imaging. [Am I goes to be happy with anything else?]
My requirements for auto guiding/fliters will largely be set by my choices above. Ideally a simple wide-field rig [e.g. Esprit/RA] paired with a narrow-field rig [GSO/533MC] would work - but that is beyond my budget. Do I choose one of the other, or go for the compromise [RASS+ZWO].
Grateful for any help… or even other options that I have foolishly overlooked.
# 27 Jun, 2020 12:39
I’m roughly at the same stage as you, so it will be interesting to see what advice and recommendations are made. Good luck.
# 27 Jun, 2020 13:48
My vote would be for the refractor. It’s the safe option and sure to produce incredible images.|
The camera seems more difficult. Any of the options could be good. Obviously the mono camera will be the most flexible, but the cost of all the extra filters will be non-trivial and the set-up/learning-curve is the hardest (I am planning to get one this fall or winter myself). You might consider if you pick this option that you can certainly continue using your Canon with the Skywatcher sometimes too? Or even get it modified unless you are using it a lot for other photography also?
My only other thought is if there are particular astronomical objects of a certain size you most want to target? That might help set what FOV seems best?
sometimes too many choices are worse than too few I suppose…
# 27 Jun, 2020 14:37
I also recently made the step from unmodded DSLR to dedicated astrophotography CMOS. For my first rig I chose the ASI1600MM Pro, an Esprit 100ED and an iOptron CEM60 and i am really happy so far. Such a wide field setup is quite forgiving when I comes to guiding during long exposure times and is really suited for most emission nebulae and also the larger galaxies and PNs. The Esprit has an excellent image quality for its price and the ASI1600 is easy to handle and a great entry to monochrome imaging. Of course monochrome imaging is more time consuming (and expensive: filter wheel, filters) and also not that easy when it comes to processing, but the possibilities with such a camera (e.g. narrowband compositions) really outweigh the disadvantages in my opinion. So my vote would be the Esprit + ASI1600 as I was at the same stage half a year ago and decided for exactly this setup
# 27 Jun, 2020 18:52
I am another newbie just starting down this path, so I don't know if I am in a position to give advice. For my situation I would avoid getting a lot of new gear each of which has a steep learning curve. If I were in your position, I would put a wide field APO refractor and a decent astromodified DSLR or mirrorless camera on that EQ-6 and just enjoy it for a while. My equipment is at the low end, Celestron AVX, a SkyWatcher Evostar Pro ED80 doublet and 2 Canon DSLRs–a T2i (APS-C) and a 6D (full frame). On a good, clear night with a clean polar alignment, I can get 180s unguided exposures. I will be upgrading–autoguiding when the backorder situation at ZWO is over and my $105 used T2i just got shipped off for astromodification. The sky is full of amazing targets that fit nicely in the field of view of one of my cameras. And I never felt completely overwhelmed trying to learn too many new things all at once.|
Clear skies and stay healthy,
# 28 Jun, 2020 02:08
Thanks to everyone for such great advice so far. There is also comfort in knowing that there are others is a similar position to me (John). The "one step at a time" (Jim M) approach is good advice, and that step appears to be (predominantly) the refractor step (Matthew, Benjamin and Jim) Add to that, modifying my existing Canon 6D.|
I can then make the next step to the ASI1600MM (Matthew, Benjamin) with this rig if I want to go all the way.
# 28 Jun, 2020 02:16
|Best of luck, I look forward to seeing your images here.|
# 28 Jun, 2020 18:10
To add on the „one step at a time“ concept…|
Astro equipment usually has a tremendous resale value. If you buy the APO refractor now, nothing will stop you from selling it again in a year or two to get that RASA or RC scope. If you tend your equipment carefully, you’ll get back 70-80% of the money, which will be of big help to finance the next scope.
I am quite a noob, but I think getting the APO refractor and keeping your DSLR will make you happiest. You can always upgrade to a cooled cam later.
Did you research the Ha sensitivity of your 6D? Many DSLRs are only at 10% transmission at 656nm, but some are at 25% or even higher. That makes a huge difference. I am lucky, my D3400 does 25% which is not that bad.
# 28 Jun, 2020 18:41
I made the same switch (from StarAdventurer + DSLR with large lens to proper mount with telescope) about one year ago. I stuck with my Nikon D7500 which has a crop sensor, not as large as full frame but obviously huge by astrophotography standards. I would like to share with you my main "discovery" and source of frustration during that year:
The reason your Canon lens costs so much despite being only 200mm is it has 9 optical elements and is designed with sub-millimiter precision to deliver an image almost free of aberrations across a large DSLR sensor. Most telescopes cannot do that, no matter what their makers claim. The Esprit can definitely not do that. Like with all refractors, you will have to add a field flattener (please note that you have to add a flattener anyway, it is not really optional with refractors unless you are doing visual or you have a truly tiny sensor, so do factor that into your budget). Without it, stars will be deformed outside the central 500-700 pixels of the image. Even with the flattener, unless you space it really really perfectly and somehow get rid of the slightest axial tilt (no adaptor clicks as perfectly as a Canon lens, no astrocam nosepiece is a perfect fit for your telescope), the best you will get (at f/5+) is an approximation of how well the Canon lens can work with a large sensor at f/4.
So unlike conventional wisdom, a smaller sensor is not necessarily a problem. The smaller sensor covers the only part of the larger sensor's field which you would keep, cropping anything else in your post processing. The difference is you won't have to store and manage 4-5 times more raw data with all that junk which you must crop after calibration.
That aside, I agree with the others that you should go for the Esprit. The RASA is not a compromise. It has outstanding light collection abilities but is very specialized. Can only be used for astrophotography with an astrocam (not DSLR) and no filters, needs its own power supply, is prone to dew, takes a while to reach thermal equilibrium, is larger in weight and size. The RC is probably the most "professional" option with the potential to deliver the best images, but its collimation is tricky and it's easy to ruin it (not irreversibly, but enough to spend the next couple weeks trying to bring the collimation back to a half decent state). With the refractor, you will spend more time imaging and less time trying to set it up. And it is the most flexible option: DSLR, OSC, mono, visual, planets, deep sky, a barlow, a reducer, you name it.
# 29 Jun, 2020 02:16
D., Many, many thanks for that very helpful and encouraging post. I do note that the Esprit 100 apparently comes with a flattener that will, at least, cover area of crop-frame sensors - if not a full frame. I may initially persevere with my Canon 6D on the Esprit to assess image quality to see if I am wasting my time with a full frame sensor. If so, I will likely go to the ZWO colour or mono camera option, where I can trade off the (unnecessary) sensor area for QE.|
# 29 Jun, 2020 05:32
|You've got an awesome new mount coming, but for anybody in a similar position with a smaller budget, I just wanted to put in a word for guiding on the SA. I primarily image at 200mm, and I get 4' exposures and a 0% rejection rate. I use a cheap 50mm guide scope and a planetary camera. You will need good PA, but with your guide camera you can drift align.|
# 29 Jun, 2020 06:19
Tyler, A very good point about tauto-guiding to take out SA ger errors. I ordered an ASIair, plus AG and scope from ZWO two months ago - but only the ASIair has turned up to date. Even without the AG the ASIair is brilliant - I can polar align to 2arcmins within 5mins. Otherwise my eyes are too old to see the Octans asterism in the SA reticule! Even if I had the AG I would probably be looking to move up in aperture and sensitivity. But if I had a more limited budget, it is exactly what I would do.|
in passing, I guess I am little bit put out by SA folks not be more explicit about focal length limitations on their SA mount . While they are clear about weight limit (although you also have to know that you need to halve it!), they don’t say you will really need autoguiding beyond at focal lengths beyond 100mm.
# 29 Jun, 2020 06:24
hi Jesco A really good point. I did try but couldn’t find anything online. Do you know of a site?
# 29 Jun, 2020 06:37
I would asdd that the only thing I found was a cloudy nights discussion where the tranmittance|
of the filter at Halpha was asserted/assumed to be around 25%. The same as the Canon 400D.
When combined with the Bayer array and sensor QE the efficiency is 2-3% at Halpa. Now a modded DSLR should raise that by a factor 3 simply from removal of the filter.
From comparison between my images and these taken with modded DSLRs on this site, I would say that is about right. (Although that is very subjective)
Of course, going to a CMOS will raise it by further 20% for a colour device and a factor 3-4 for a mono CMOS at the expense of additional filter onsetvtinns). That’s the thing about this grey hobby, it’s knowing when to stop…
# 29 Jun, 2020 08:42
I'm also wondering how my longer term equipment plan could look like. As I'm currently working with a Samyang 135 mm f2 lens, I really wouldn't like to give up fast focal ratios when going to a bigger scope. So every now and then, I screen the market a bit.
These are my favorite future options until now:
What about something like this? However, I'm not sure if it's available in your country. Nevertheless, from your budget pov is should be ok and I have seen great pictures taken with this scopes here on Astrobin. They feature fast focal ratios of 2.8 or 3.2 combined with a fully corrected 44 mm image circle, suitable for full frame cameras.
# 29 Jun, 2020 09:00
Steve, Thanks so much for bringing these to my attention. You have given me another serious option to think about.|
Based on the comments above, I guess my only worry would be whether I would need to spend a lot of time collimating and get frustrated
due to my ineptitude.
But it certainty fits the bill with aperture, speed and full frame compliance. Those spot diagrams look impressive considering a 5.7um pixel.
# 29 Jun, 2020 09:26
Large apertures do not forgive collimation errors. I don't think it is a showstopper but you would definitely have to buy a laser collimator and collimate after every session.|
I think an F/5 Newt (130/650, 150/750 or 200/1000) is the best balance between speed, aperture and operational convenience. And price of course. By far
# 29 Jun, 2020 09:28
Maybe it's a good idea to ask actual users of this scope whether collimation is an issue or not.
According to the search function those two guys used it regularly with great results.
# 29 Jun, 2020 10:49
Steve LudwigBrian Boyle
I think another point is that people sometimes might overestimate the effect of collimation. I would even say that some people that warn others about the "the outstanding difficulties" of reflector collimation, not even own a reflector. They just repeat what they have read elsewhere and stick to their slow and "safe" refractors. I really don't want to offend anyone, but I think some of you might agree that there's a little truth in that.
Let me show you my first ever astrophotograph. I did that some years ago with my 10" f/5 dobson, without knowing anything about collimation. Shortly after taking that image (800 x 0.5 s short exposures cause I didn't have a tracking mount), I realized that my collimation was far off. The secondary mirror was tilted so much that only around 60% of the light reached the sensor. So, the left half of the sensor was illuminated, with massive vignetting towards the right hand side of the sensor. The center of the image circle must have been somewhere around the left edge of the sensor (APS-C size -> Nikon D3300). It was actually a total mess because I simply used the scope as I received it. Below you find the image I got. Despite the normal coma (I didn't use a corrector) and some star trailing (as 0.5 s exposure time was already too much) the image is fine and not too bad for a first try. I just wasted some light. That's it. After a proper collimation done right after that, I now use my dobson for more than 2 years without any readjustment needed. I even gave M42 another try with proper collimation. I expected a lot from that experiment, due to all the comments I read about the "importance of perfect collimation". The result was that I got exactly the same image as before.
Of course the effects might be more severe with an f2.8 or f3.2 scope, but I would expect it to be manageable.
# 29 Jun, 2020 10:58
I am somewhat surprised to see you are already considering spending so much money (let alone time, sweat) after just 2 months. There are 10 more months in the year with objects to picture using your setup. This also provides time to improve on post-processing.|
My advice would have been to stick with what you have for a while longer. (Prior to getting the eq6). Then again… using your DSLR on the eq6 for much longer exposures is also an option.
With whatever you choose, remember it is a steep hill to the top, but remember to have a pause every now and then and look around to enjoy the view!
# 29 Jun, 2020 11:15
Steve LudwigSteve LudwigBrian Boyle
The spot (or circle) in the focal plane where the image of a Newton reflector is coma-free is pretty small. For visual use, we want to be pretty precise in collimation, making sure this circle is aligned properly with the center of our view through the eyepiece. In fact, the size of this spot shrinks with the cube of the focal ratio. So, in this sense, properly aligning the mirrors is 25% more difficult just going from an f/5 to an f/4 Newton. See also https://skyandtelescope.org/astronomy-resources/how-to-align-your-newtonian-reflector-telescope/
For imaging similar arguments hold. Of course, it depends on many things, such as image scale, tracking error, etc. which is the dominant factor. Also how much you care yourself. Where do you set the bar? How “perfect” do you want your images to be (if there is such a thing as perfection here)?
In any case, there are many reasons for the advice to start imaging with small, fast refractors and not with bigger reflectors. The number of imaging sets gathering dust around the world because of underestimating the effort required, must run in the thousands, if not tens of thousands. I think it is therefore unwise to disregard it.
# 29 Jun, 2020 11:38
Victor, wise words indeed.
Your comment on post-processing is particularly insightful. This is one area where i do struggle - not with the concepts but with the artistry of what is done here. Your words are a timely reminder of an area which I plan to improve in - over the 6months or more lead time to order this kit (at least so I am told by my supplier).
[A significant factor in the delay is time NZ customs are now taking to clear imports. NZ’s success in eradicating COVID19 has understandably made customs here all the more hyper vigilant on people/imports from other countries that, to date, have been less successful. Still waiting on an astronomy atlas from S&T, 3months after it was dispatched]
By that point, I will be 8-9 months up that hill, and perhaps looking for that slightly clearer view when I get to the top.
# 30 Jun, 2020 00:20
I would vote for the 100mm refractor, a nice light scope, and it could be a workhorse. I recently bought an even smaller scope and am really pleased with it. (StellarVue 70t - two thumbs up)
With almost two years under my belt with an unmodded DSLR, I am at the same stage for camera selection and so this is a very interesting thread for me.
Kind regards, Ian
# 30 Jun, 2020 05:40
I am pleased to hear than others are finding this thread as helpful as I am.|
At Steve's suggestion I contacted one of the Hypergrpah owners (Okke) who take such great photos. Since he also takes amazing photos with another of my options (a large RC) I also asked him about that. He clearly loves both - referring to the Hypergraph as a rocket - but also notes that rockets can be temperamental. He confirmed the challenges around (re) collimation, but also enthused about the reward for getting it right. He also waxed lyrical about the RC, but the more he explained the more I felt that the step-up might be too much for me.
I also like Ian's comment as the 100mm APO being a workhorse. I might go light on the imager (or stay with my unmoved DSLR) until I decide which thoroughbred to invest in, after a few more years experience with the Esprit.
# 30 Jun, 2020 09:21
I have to disagree with you. I did own a reflector. The infamous Celestron Astromaster 130, which was also my first scope. Completely unsuitable for astrophotography I admit, but my specimen had such horrible optics (perhaps it got shaken badly during transfer?) it was very difficult to get a decent image even in visual at the lowest magnification. I didn't even know collimation was a thing, I found out about it while trying to figure out what was so wrong with my scope. And then I tried to collimate it which is not much fun if you have an EQ mount and all your big stars happen to be in inconvenient parts of the sky and the merest shake of the scope moves them away from the FOV. I did manage to bring it to an acceptable state but of course I lost half of that evening and of course a few days later it had lost the collimation. And that next time I collimated it I wasn't so lucky, I tried hours and hours and only seemed to make things worse every time I turned a screw until I just couldn't stand the cold and declared defeat. I have never used that scope since that night (December 2014 if memory serves me) and in fact for the next four and a half years I stayed away from telescopes alltogether, opting for my Nikor 35mm f/1.8 for wide field and the Samyang 135 f/2 for large nebulae. Even for visual observation, I preferred to use the Samyang and Live view as a form of quasi EAA.
I fully appreciate collimation is not so difficult (at least for Newts) if you have the right tools and have practiced somewhat and are not a complete tools like I was and your optics are not pathological to start with, but coming from the camera world I am more used to the optics just working or not working because they are unsuitable for your intended use, in which case you trade them for something that is suitable. We are not so used to having to tune the camera lens as if it were a guitar, we are used to it simply working like a harmonica. Refractors and other designs such as the Mak usually won't need any tampering with. They are pre-collimated in the factory and tend to keep the collimation for decades. They are like harmonicas. RCs are an interesting case because they do keep their collimation much longer than Newts but they will need it eventually and it is difficult to get right. They are like pianos I guess: only need tuning once every few hundred sessions, but that tuning requires good skills and is usually done by experts.
Switching from harmonicas to guitars and pianos is not a bad thing of course. But I wanted to highlight that extra aspect of difficulty for Brian because it turned out to be a very nasty surprise for me, coming from a DSLR background. His initial ranking of telescopes took almost exclusively aperture and focal length into account (like one would with camera lenses), I think with telescopes other factors like weight, thermal stability, uncorrected performance and of course maintenance are equally important and this is what I wanted to highlight.
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