Quote:
Originally Posted by gregbradley
My experience with full frame sensors is you need 3 inch plus focusers and accessories. That was with an STL11 camera and a Tak FS152. Taks' 2.7 inch focuser and accessories vignetted badly.
As you say you could test it out with a full frame DSLR or mirrorless camera easily enough if you can mount it. Its more the correction so the corner stars are pinpoint rather than vignetting. Vignetting is fixed with good flats. All my scopes need that anyway. But if the correctors don't have a large enough corrected circle (44mm for full frame) then you are going to have to crop a significant part of the image so you may as well have used an APSc sensor in the first place.
The variable slightly dark lines in the darks would process out if the sensor were dithered. It also may not show up in an image anyway as its quite dark and background and not very bright. I did have trouble with a grid pattern noise with my Trius 694 camera sometimes. A good bias used to fix it.
These type sensors probably don't even need darks as there is hardly any noise in them. Perhaps just a bias or nothing at all (perhaps a flat).
Greg.
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So with my 125SDP (616mm F4.9 with reducer), I'm getting Josh to make up a M84 on the OTA end but unfortunately for ZWO's tilt adapter design, it's still only M54 on the camera end. Not to mention there's a further 50mm (excl the tilt adapter) to the eventual sensor (the OAG, and 2" FW in between). Although I've not gotten the adapter from Josh yet, I'm pretty sure even with 125SDP's 88mm image circle, it'll vignette due to ZWO's use of M54 in the tilt adapter.
Even with my Takahashi µ250CRS (2500 F10) with a 40mm image circle, I have an M72 sized adapter on the OTA end and and M54 on the ZWO end. I believe it'll vignette more than my full frame CDS A7S (which is a straight M72-M72).
QHY600 OTOH sounds interesting that they have a special short flange version. I don't know the size of QHY's FW/OAG to see if it's more susceptible to vignetting even at F10.
Back to the ZWO though, I've read some folks are custom widening the tilt adapter from M54 to M68. Maybe that helps a little more however the filter is still 2".