My new OTA mounted up and ready to go on the CEM120. This is my first foray into longer focal length imaging and also getting re-aquainted with SCT collimation etc.

It’s never smooth sailing with any new gear, and this was (and still is) no exception; although so far I’m keeping my head and enjoying the challenge.

Thought mounting my "Prima Luce Lab Eagle PC would be easy given that nice vixen dovetail socket on top… well the prima luce lab vixen don’t fit…nor did another cheapy vixen I had… fortunately the vixen plate off my Askar 400 did fit so swapped the prima to it and vice versa and voila.

Thought the Prima ECCO dew controller would fit in the finder holder…nuhuh… must be some Meade proprietary thing… managed to jury rig a solution. 

Carrying it out and mounting on the CEM120 was a bit of a struggle… clearly Meade, as with the top dovetail, follow their own road on sizes for the Losmandy style main dovetail as well (or Ioptron do); it took a number of attempts to get the dovetail to slide in while struggling with the weight… really felt for a while it wasn’t going to fit, and almost gave up (my back has!), but with a bit of WD40 and coming in from the side finally coerced it into place… Phew! The Geoptic dovetail I have slides in easily.

I made up a temp dew shield using one I had for an old C9.25…taping up a seam to get sufficient diameter for the 10in and a full round dew strap controlled by ECCO as far forward on main body as I can get behind dew-shield… this time of year not much dew about but stayed dew free anyway. I’m getting some reflectix insulation to wrap tube as well.

Only did the most cursory of collimation so far. Main aim first has been to get mount and guiding calibrated and see how my system manages 2m focal length. Was already using an OAG so nothing new, and guiding was actually remarkably pain free with tracking most of the time sub arc-second.

While learning this scope I'm using my smaller ASI294mm and (Antlia SHOLRGB filters) which has larger pixel size (4.63) than my ASI2600 and hoping with smaller sensor will be a little more forgiving for collimation etc.

Initially I had my imaging train as crammed up as possible to try and get as close as possible to nominal backfocus (I know it can work much further out, but understand correction and full FL is best at ~115mm or 109mm (depending on who you believe)… I was pretty close to this but another 5mm from focuser travel. An unfortunate side effect of this cramming is I couldn’t get my guider camera close enough using helical focus adaptor to match main camera focus …had to use the non-helical and it was still a little off… but worked. 

Focusing has been the biggest headache …I fiddled with so many settings in NINA and the Esatto that first night to try and get reasonable focus curves and after 2 hours almost gave up… I finally tried some big Backlash values (8000) for Overshoot method and set to Hyperbolic only and bam started to get good curves at least for LRGB... has since discovered for Narrowband at this FL at F8 probably need much longer exposures than the 5-8s I normally run. Have some tips and tricks from Patriot Astro to try including NINA's Hocus Focus plug in to get this dialed in better.

Even at good focus it’s clear there’s some work to be done with collimation, and maybe tilt, maybe guiding, maybe sub-optimal backfocus such that coma correction not as good as it could be … stars pretty poor shapes from centre to one side. I have a program Metaguide I am going to try to help with star collimation, but need to read the manual! Of course I’m used to refractor stars and at a third the focal length so may have unrealistic expectations on how round and tight stars can be here.

Not expecting much I setup a LRGB_Ha sequence on the Galaxy NGC253 at midnight that first night before retiring to bed, and was pleased to see  in the morning it all worked, including flip and was still happily tracking at 5.30am. I pointing the scope up and a white T-shirt over and did some flats (lots of dust motes and weird asymmetric vignetting on lights and flats I’m not sure the cause of (checked it’s not the dewshield) and ran the data through APP and some Startools processing (had to bin 50% for better S/N as only a few hours data) and tweaking in PS using my usual starless processing methods and reintroducing and got the result attached

Considering all the struggles and poor seeing, poor looking stars in lights etc. I’m encouraged…there’s no doubting there’s more detail to be had here than I have managed with my 5in Apo - if you look in my gallery I imaged NGC253 a month or so ago with the apo and with double the integration time as here and I think this is a fair improvement on that.

I’ve since stripped down my imaging train, cleaning and re-seating everything and extending camera backwards ~20+mm (which also seems to have resolved that wierd assymetric vignetting) so I can use my helical OAG focusser – with this I'm  at around 140mm to the sensor from the back thread and a FL of 2130mmm (so longer than nominal 2032).

Next step will be sorting the collimation with Metaguide... just need the sky time. Ideally I'd like to swap out the Esatto focusser with an Optec Direct Sync (If it ever comes in stock) that fits to the OTA's native crayford focusser ... I like the esatto but it's taking up nearly 3/4 of the available OTA backfocus. At some point will likely also try with an 0.67 reducer, but want to get thinks working at native first.

UPDATE 22-09-2022 - i ended up returning the 10in due to astigmatism and upgraded to the 12in Meade OTA and have been using that for all recent images