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Showing results for tags '135mm'.
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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. CS. 6 x 600s (1 Hr) Atik 383l+ 2" Baader Ha 7nm Tamron Adaptall2 135mm F2.8 (@F3.65)
Help! 80% of 115 60-second RGB subs with Zeiss 135mm f3.5 Sonnar. I know I have basically got some really good RGB data here, but I seem to have a problem with red stars. I've done what I can but I am sure I can do more. I also need to look at ways of reducing background noise further. I'm trying a second stack without bilinear debayering.
Sometimes the weather gods look on you kindly. A nice new Samyang 135mm turned up from that well known jungle supplier, I managed to assemble it to my Atik 428ex mono along with an Ha filter and got the spacing correct, and low and behold the skies stayed clear - all on the same day! I am sure there is room for improvement with the processing but this is IC1396 processed in PI; STF applied with HT, and a little HDRM + LHE to try to tease out some detail. Any help on improving the processing would be gratefully received - I really don't feel I get the best out of processing mono images. By the way this is 12x300s + 10x600s combined with HDR process in PI; flats, no darks and a master bias. Thank you for looking. Adrian
Hi I have been thinking about having a go at widefield stuff for a while and wondered if anyone could recommend a used decent camera lens to look out for on ebay etc. I would be using my QHY163C with it I currently have an Altair 102 triplet and a megrez 72 (sold my 8"RC last year ...still keeping an eye ot for a C9.25 to replace it for planetary/luna etc) on a Mesu 200 mount It would be used for wider stuff than I can get with the Megrez 72 ...say...the Heart and Sould Nebs in the same FOV. Just thought it would be something to try if I can pick up an old camera lens for a resonable price ....is a zoom worth considering? ...camera resolution is quite high at 3.4 size pixels so is a fixed fl better then crop after etc. Never done any AP with a camera lens so am total virgin with them....any thoughts/recommedations to put on the shortlist gratefully accepted. Tom