festoon

Another +1 for the canon lens is that you can use a filter wheel with it.

Fantastic to hear that someone is using this lens for imaging. And it’s really great information regards the versions. At 4.5kg it’s still significantly lighter than a RASA8. Do you have any images that you please can share? Now I’ll have to start looking out for these second hand

As a fellow Physicist I'm loving this thread keep it going I'm learning a lot from the discussion thank you to all the contributors.

Had to check it out myself, and learned that there are 3 versions of the 400mm f2.8 lens, the latest being the lightest, with the first Canon lens designs featuring new glass materials. "This glass has a comparatively higher refractive index than general low-dispersion glass, and has a low specific gravity. By using the new glass material in the first, large-diameter lens element [which cannot be reduced in size due to the focal length and max aperture requirements], the weight is reduced and spherical and chromatic aberration are suppressed."

Yes the technology of the lens itself is pretty amazing. It would be cool if Canon sold 'for astronomy' rejects with non functional IS or focus

There’s even a photo of the setup similar to what I was thinking of in this post

Phew! Yes just think how much that rig cost to build. What a fantastic project to work on!

Sorry had to post this picture from the gallery

Wow that is awesome! That is one amazing imaging rig!

Thanks @Alien 13...I have never heard of the dragonfly project...what was that?

@catburglar, yes with my Samyang 135mm I do get sharper images when stopped down slightly, but with the effect of introducing diffraction spikes. Do you not get a similar effect on the RASA with wires from the camera crossing the optical path?

Thanks @newbie alert Sure, and in this case what I was wondering is you have two optical systems with the same focal length and a similar aperture. One is designed and well known as an imaging scope (the RASA). I was wondering if you could get comparable results from the canon?

Is there an issue with discussing f ratio and imaging?

Found some wonderful images over the past few months of users imaging with the RASA 8 scope. And when paired with an APS-C sensor giving amazng widefield shots. If I ever get the time to set up a perminent imaging set up and observatory, I'll probably end up buying a RASA. Probably a stupid question, but I was wondering would there any comparison if you had a Canon 400mm f/2.8 lens or a similar lens? Its a fraction of the weight (2.8kg vs 7.7kg) and no central obstruction. The usable diameter of the RASA is still larger with an effective diameter of 180mm compared to 142mm and the RASA is optically faster. Probably the reason this is not compared - The price of the Canon lens is significantly more £12,000 new compared to the RASA at £2000. However, I've been amazed with what I've seen using the Samyand 135mm f/2 lens and just out of curiosity what are your thoughts on the question?

To test it you can use the camera simulator and use any image eg from your previous imaging or even an image file from SGL and ask it to solve it Glad the fix worked. Don’t know why G17/18 database is needed over H DB but it’ll at least you are making progress

If you are on windows go to programs (where you install and uninstall programs) find the star directory and click uninstalll

I had the same problem and when I installed the g17/g18 database it then worked fine. Try uninstalling the h databases and install the g database and see if that works. If this does not work, the other things you can try are increase search radius to 180 degrees and set down sampling to 0 or 1

Just noticed the amazing price on the FC-100DC at 191,000 yen. That’s only £1200 back in 2016!!!!! Amazing photos, thank you for posting, it must have been a great experience!

Looking at the data...the walking noise is much better after 1 hour of 3 second exposures data compared to just 30 mins Lots of detail in there so quite happy with the result.

Thanks @vlaiv. I guess I never appreciated how sensitive the setup is. If I went for another sensor like the ones I put above would the sensitivity be reduced compared to what I have now? I'm not sure about the physics behind fixed pattern walking noise. I guess the effect is more prominant at lower exposure times as the SNR is lower. If I decrease the gain setting on my setup, will walking noise be the improved, get worse, or be the same for a given exposure. My thoughts are it would get worse. I think overall I'm limited by the dymanic range of the sensor to detect faint and strong signals at the same time. If I decrease the gain to zero, the dynamic range will increase slightly, the full well increases to 19k (x4 improvement) and the noise only increases by x2.5. So I'd have an overall dynamic range increase of x1.7.