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A few months back, i bought my first mono camera, an Atik 383l+ from Martin @Xsubmariner off here. I hadn't had a chance to give it a whirl until last night.
I thought about getting the 80ED out, but i've been wanting to do some widefield stuff for a while, so i attached an old Tamron 135mm F2.8 vintage M42 lens i picked up last year for next to nothing. The lens needs to be stopped down to F5.6 (perhaps less, i haven't tested though) to produce acceptable stars in broadband, but i was hoping it could be used more wide open for Narrowband. I used step-down rings screwed on to the end of the lens hood to bring the aperture down to 37mm, which is about F3.65 (i did briefly try it wide open in Ha, and it wasn't that bad tbh, but i could still make out some comet-shaped stars in a few places so i opted to stop it down a bit to play it safe). I have a TS Optics filter drawer in the optical train, so i can still swap out filters without too much fuss. I still have about 3-4mm of extra backfocus space to spare, but i can already find focus as it is, so i'm not sure if it's that important that i haven't fully used it all up.
Focusing was tough. I was focusing using a Bahtinov mask on Deneb, and i had to use 10s subs (subframes) at 2x2 bin to get bright enough spikes for Bahtinov Grabber to pick up to the spikes ok. Even then, it was showing the focus error moving about quite a bit, even without me touching the focus ring. In the end i just got it as close as i could and went with it.
Conditions were not great. Some clear spells, but there was a lot of cloud passing through. I figures it would be good enough for a test session. The Phd guide graph looked horrific, and was somewhere in the 1-2" range (image scale is 8.4" so not a big deal hopefully). I bodged together a couple of old dovetails to add enough weight to counter-balance the 5Kg counterweight. It just about does. It's not perfect by any means, but hopefully sufficient for this purpose.
I would ideally like to shoot 1200s subs, but couldn't last night due to the constant clouds (Phd lost the guide star countless times). I was about to give up, but persisted and aimed for 600s subs. Glad i did, as i ended up with 6 useable subs, even if a couple were affected by some thin cloud.
Did a quick stack in APP and a 10 min process in PS, just to get a rough idea of what i can expect from this. I used Flats and a couple of Darks just to do a rough calibration. Didn't do any gradient reduction, was in too much of a hurry after packing up last night. Overall i'm fairly pleased with how it performed. I'm obviously not aiming for Samyang 135mm F2 levels of performance here, but for purely NB bi-colour mosaics i think it can do a job.
I've included a picture of the rig below as well, in case anyone's interested.
6 x 600s (1 Hr)
Atik 383l+ 2" Baader Ha 7nm
Tamron Adaptall2 135mm F2.8 (@F3.65)
This was 3 night's work with a Takahashi Sky 90 on a self-guiding Vixen SXP mount from the back yard. I used a triad filter on a Canon EOS Ra at ISO 800.
157 x 5 min subs = 13 hours integration time (my longest yet by far)
Processed in PI and PS. I drizzled again (sorry Vlad - I just can't help myself) and was pretty happy with the level of detail from a 407mm FL.
The wide shots show a fair bit of astigmatism in the corners - but I thought the Sky 90 did pretty well. The Vixen SXP is a dream to use - it's lovely to be able to do the entire thing without a laptop. Annoyingly I had the mount in the wrong mode (Dec off) for 2 nights so the stars are a bit eggy, but I didn't have the heart to throw out the data.
I think the smallest crop is a bit reminiscent of the dementers in Harry Potter.
* Edit - I had another go at reprocessing this. I think I left the originals far too muted. I redid them as LRGB, with the red channel (HA really) as the luminance layer).
Thoughts anyone? Better before of after?
This is from a couple of nights ago.
It clouded in quickly, so I didn't get much data. The temp was 2C, and I'm self-isolating - so that was also a factor! I only took 5 darks before I gave up and went to bed. I'll take more when the temp is right.
This is 140 min integration time on a new Canon EOS Ra with 17x500s exposures, and no filter (from the city).
Processed in PI and Photoshop - I should have used more star masks but the data aren't good enough to warrant the effort I think. I also had difficulty with flats - I tried a range of exposures with a Gerd Neumann panel, but I think they were all too short. Will go longer than 0.3s next time - very hard to figure out flat exposure on DSLRs, and APT's tool doesn't work for DSLRs yet.
I think I'm obsessed with M51 - and I know I'll be back to it again.
Stay safe everyone,