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Hi All, I was looking at this and though I love the idea of ditching my guidescope on my epsilon160, I'm trying to fathom how significant a change this would be. (since I already use an asi2600mm) I've noted that wider narrowband filters would also be required (something in the 6-8+ nm bandpass). I'm also thinking that my image sequence might need to evolve. I usually do a sequence of 3-6 exposures with each filter cycling through. That doesn't require stopping/starting guiding, but with a camera like this behind the filter, maybe it would? Looking for any practical knowledge of using these DUO's. thanks and CS Nick |
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I had difficulty tracking through RGB Optilong filters with the ASI2600 Duo Mono on a Celestron EdgeHD 11" and OAG. I suspect that this would work best with a color camera at shorter focal lengths. |
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Bill Becher: thanks Bill, was the OAG unused but still in the optical train? assuming you were at the native F10, I could imagine that being difficult. I'm planning on 530mm FL, so hopefully that would be a sufficient amount of stars? |
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Nick Grundy:Bill Becher: |
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I'm guessing there's a decent lumination fall off at the edge of the image cirlce under a filter (they cite a 42mm circle) combined with the focal length makes it very tough on guide star selection In contrast, does the OAG perform well for you? (seems like it does most with the edge11) |
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Nick I have had better results with an OAG on the edge11. I tried the Celestron OAG but the ZWO OAG L works better probably because it comes later in the optical train and gets more stars. I am using the ZWO 174 guide cam as it has a larger sensor. Getting the backfocus right with the edge is the problem I ordered a custom adapter so that I can use the Askar backfocus adjuster to fine tune the backfocus. I sold the Duo |
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I think it's fair to say the 'Duo' cameras were designed with one user in mind.... The RASA user. Beyond that, I can't comprehend why you'd ever want one. It's not the greatest idea. |
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FYI, i bought one of these (despite Brian thinking its terrible idea) and am pleasantly surprised. In a situation where you don't have the backfocus for OAG, but want to keep the load lighter, it works well. a couple notes though
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Brian Puhl: Paired with RedCat71 - it works well |
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Jeremy Jackson: definitely! I actually had mine on my redcat51 |
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Nick Grundy: I have a question that is a tiny bit off-topic I've always wanted a Blue Fireball rotator on my newt, to frame my objects better but my backfocus doesn't support it, because I have a 17.5mm backfocus camere, an OAG and filter drawer, all of which takes up the whole 55mm backfocus I have three options: 1. remove the filter drawer and attach my filters to the outside-facing filter thread on the coma corrector 2. get a Rowe coma corrector and keep the OAG and filter drawer 3. keep the current coma corrector and the filter drawer, remove the OAG and use a 2600mc duo instead all three options would give me enough backfocus to use the rotator which would you (or anybody else) choose? |
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17.5mm backfocus camere, which camera are you using? I know you can remove the tilt plate from the ZWO cameras, which gets you another 5mm. (though I don't know how the filter drawer attach then) I was already in the market to get another 2600mm, so the DUO made sense for me. Buying the camera just to deal with the backspace, seems like an expensive solution. |
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I've seen reviews where people have guided perfectly fine through 6nm narrowband filters with the duo. The question is, how does your mount like to perform? I can happily use 3sec guide exposures, because the periodic error of my mount is low frequency and very low amplitude... I know that harmonic mounts suffer from eratic, high frequency and reasonably/very high amplitude periodic error, so people typically require 0.5~1s guide exposures to tame them nicely. Not sure you'd be able to run a 0.5s guide exposure from behind a 3nm Ha filter (unless your optics are REALLLY fast) I'm considering a 2600MM Duo for my rig, but again, I can run 60s unguided exposures with less than 1 arc sec of drift, so I can run 5 sec guide exposures, or stack multiple 2sec guide exposures and maintain a perfectly acceptable level of precision.. |
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Nick Grundy:17.5mm backfocus camere, asi533mc pro it's actually 6.5mm in the camera itself but with the 11mm ring that comes with the camera, it's 17.5 the rotator takes up 13.5mm |
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Nick Grundy: You pretty much noted right here why I think it's a terrible idea  Unless you have a high end mount, you need reasonably fast updates to account for periodic error. Especially this day and age with all the harmonic mounts being the craze. Portable or not, they have some of the worst periodic error of any mounts on the market and require high speed updates.
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| Hi Nick - I'm using the ZWO 2600MC duo for almost a year now. First with a RedCat 51 on a StarAdventurer Gti followed by the ASKAR 103 Apo on the ZWO AM5 Mount with harmonic drive. With both settings the 2600MC duo is controlled by the ZWO AsiAir Pro and I'm very pleased with the guiding. I'm also using filters like the Optolong L-Extreme and with some fine tuning get excellent results from my point of view. |
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Brian Puhl: I think that's probably the most notable caveat. Don't use the DUO with tight narrowband filters if you also need short exposures in PHD2 for guiding. I tested 2s guide exposures last night with the DUO with Optolong SHO 3nm filters. Ha was definitely problematic depending on where in the sky i was tracking. On the HEM44EC (which is only half strain wave in RA) I bumped to 3.5s exposures and didn't struggle with guide star selection. So if you do DUO, just keep that in mind. Otherwise, it seems like a viable path if you don't have the backfocus for OAG |
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| My duo works great with a redcat 71, AM5, and 3 nm Optolong L-ultimate filters. I have to use a guide camera setting of 350 gain (with dark library) and 2 second exposures, but still manage to guide around 0.75" on an average clear night. On a great night, I've seen guiding down to 0.3" to 0.4" |
