Hey guys, it's been long since I have been here!

Meanwhile I found a way to adapt my Pentax glass to the ASI CMOS astrocam with the filterwheel attached!!



I just tried it out and the setup gets into infinity focus for all my Pentax lenses. This adaption only makes sense for lenses that have a manual F-stop ring.

If you are interested this is what you would need:

1. A slim adapter Pentax PK/Canon EOS like this one: Objektivadapter PK-EOS Pentax PK Objektiv an Canon EOS Kamera Adapter PK EOS | eBay. This one sits very tight - which is perfect against any tilt. But be careful that you remember well how you attached it because it can sit VERY tight and turning the wrong direction may cost you a lot of nerves while loosening it :-( The adapter adds 1.5 mm optical way.

2. This adapter from Canon EOS to ZWO Filterwheel: Teleskop-Express: ZWO Canon EOS Lens Adapter for ZWO filter wheels and astro cameras. Teleskop Express states there are 7.5 mm from sensor to filter wheel but at least in my case the distance is 6.5 mm. The adapter itself adds 17.0 mm optical way.

3. And a tripod/mount adapter to hold the camera. Be careful because there are two dimensions (78 mm and 86 mm): Teleskop-Express: Astro-Shop + Fotografie + Naturbeobachtung

The filter wheel adds 20 mm optical way. So we end up with 1.5 + 17,0 + 20.0 + 6.5 = 45,0 mm which is nearly the 45.46 mm that is the Pentax K-Bayonett sensor distance. You may want to heal the missing distance with a 0.5 mm fine tuning ring ( I do not know the English word for that).

I am really curious to do wide field narrowband astroimages with Pentax glasses. And I hope you agree that using Pentax lenses would be my new ticket of admission to post images here again even though the camera is another brand (do you go along with that?).

Cheers
Pete

I vote in favor of your request of returning “home” by using Pentax glass. When can we see the first result?

Come home Pete, we miss you and promise not to examine your EXIF data too closely.

[I erm, might attempt to exploit the same amnesty to post some narrowband stuff. Assuming that I can ever (a) see the sky and (b) have my stuff work. Currently struggling with plate-solving, which has decided that it does not like my ASI183.]

So yeah, post some images already!

Very nice! I've often wondered about trying to put small lenses on astro cameras.

I ended up going with the medium format option because of the required flange distance on the QSI cameras.

Good to see that you have a solution that is very slim!

You can build a robo-focus device to automate focusing pretty easily - if you don't mind the cost.

I'm curious about vignette at various f-stops, too.

Share some FITS!

Puh! Thanks guys . Yeah I really miss home and feel very comfortable here among us Astro-Pentaxians It's different and much more anonymous in the big big world out there.....


I do not know when I will be able to show images taken with the new ZWO/Pentax setup. First we urgently need clear skmies here- not those depression cyclons crossing the Atlantic Ocean to bring us rain, wind and clouds. Next I have to finish my "big" shift-roof-shelter box as a new home for the balcony pier and the telescopes. Finally I need a proper target for the small focal lengths between 25 mm and 200 mm (any ideas from your side?). But I am really curious and will use the next chance for some test. I will post the results asap.

Rick, may I ask what software you use for the plate solving and what the problems are? Maybe we have an idea here to cut the knot....

I still don*t know what will be my strategy with the Pentax lenses. At the moment I have more more scope configuration options than clear nights even just with the possible combinations of flatteners & reducers for the "real" scopes that wait for their task. I think I might use the Pentax lenses for big targets like Simeis 147 (Spaghetti Nebula) or for overview images. One idea is to combine such an overview with detailed images of DSO contents shot with the big scopes. APP will do a good job registrating the different image sources on each other hopefully. Another idea is to use the small Pentax/Zwo combi in the field for something like "lucky imaging" by shooting RGB skyscapes through the filter wheel witthout a tracking mount at very short exposure short times with high gain.

As you mention a robo-focus for the lenses I think I would invest into a second MFOC stand alone motorfocus for my 80/480 apo first.

I hope the vignetting can be killed with flat calibration. I am more concerned about fringing that showed in earlier images of mine when I was slightly out of focus. But in my understanding this green or red fringing somes from an insufficient correction of the ancient lenses. As I will shoot through RGB filters maybe this can be healed by using slightly different offsets to get each filter into focus separatela. Any ideas if this might help?

Calculating filter offset is best done with an automated focuser.

I use CCDAutopilot and TheSkyX to do all my imaging. Fully automates target aquisition, platesolving, guiding, focusing due to temperature and filter, and multi-target planning.

Yes, it all costs a bit of money, but it means that I can automate two mounts while I fiddle with film.

Regarding planning for wide field targets, there are a ton of nebula that are large. You can play with composition with a wide field - you're not restricted to the standard catalog-style shots. I use custom FoV frames in TheSkyX to help plan out my shots, taking note of where bright and dark nebula will appear.

I don't know the capabilities of this ZWO camera and if it would be a good candidate for shooting dim reflection nebula or dark clouds.

It's the astrometry.net offline solver, run from Ekos (index files from 4205 upwards; my FOV is a smidge over 2 x 1 degrees). The dream is to get the mount physically aligned, maybe do a one-star alignment to get its reported RA and DEC numbers into the ballpark, click "Capture and Solve" with the "Slew to Target" option, and I'm laughing. What makes it particularly irksome is that I've actually gotten this to work in the past, at least with my ASI120MC guide camera. Of course that depends on the guidescope being pretty well collimated with the main scope, so solving through the main scope w/b much better.

I never got it to solve an image from my K-5iis, and had trouble with the ASI183MM too. Now I think I know why: A 16- or 20-megapixel image just overwhelms the little Pi's computing abilities. Using the command line directly, I figured out that downsampling by a factor of 16, and having a starting "hint" within, say, 30 degrees in RA and DEC, was enough to consistently solve from a static FITS image in under two minutes. I also found out that if I ran Ekos on my laptop, (just running INDI headless on the Pi), and did the solving there, the high-end MacBook Pro brute-forced it at full resolution and no starting hint in 26 seconds flat. Hey, it's good to have the tools of a software developer. :-)

I tried to test this theory in the field last night, and was STILL rebuffed. I consistently had problems getting Ekos to connect to the mount. Which is particularly frustrating because that is a brand new problem, ever since I got the Pi set up it has always connected to the mount without complaint. Maybe something isn't connecting right due to the cold? I'm pretty baffled. I tried rebooting and power-cycling everything, and switched the Pi over to mains power just in case the battery was low or something. Nope. I did get intermittent connections, but never got it working properly, the software never managed to read the coordinates from the mount. Without that as a hint, the Pi never gets to a solution.

Physical setup is a Keyspan USB-to-serial adapter between the Pi on one end, and the mount's RJ-11 connector to the hand controller on the other. Curiously, it has never worked properly routed through a powered USB 3 hub, it always has to be plugged directly into the Pi. And connecting the Mac to the CEM-25P via the Keyspan has never worked either. But until last night, plugging the Keyspan's USB cable into one of the Pi's 4 USB ports worked every single time.

Have you updated Stellarmate/kStars Rick? Don’t know if you’ve seen it, but there seem to be some issues with the latest release. My Pi is still on the previous release, works fine (HEQ5 Pro mount, EQMOD driver, PC direct via the hand controller).
I’ve managed to offline plate solve using my K-70, running kStars on a laptop. The only thing is the time it takes for a single useful exposure (60sec+). Using the 50ed guidescope/ASI120 mini requires it to be aligned with the telescope, also requires a lot of trial and error. I often spend most of the time getting everything ready, I need a balcony like Peters or a proper observatory so I won’t have to install and adjust everything every time.

No, I don't think I have updated it. (I do lots of random things and don't recall all of them, after all.) I was actually going to as soon as I got home, but now I shall wait.

My updated workflow, if I can get the mount talking to the Pi again, will be to start out and set up with just the INDI server running on the Pi, and do all the setup, pointing, and solving on the Mac. Probably will do focusing with Ekos on the Pi, since that won't entail the longish download times. Once I'm ready to fire up a job or sequence to actually image, I'll run Ekos on the Pi, since that will run all night off my 12V SLA battery.

Try binning 2x2 to help with platesolving. It'll give you a smaller file to use and still be as accurate.

2x2? Hah, you must use one of them there REAL computers. I found that downsampling the image by 16 worked pretty well!

Actually I suppose that binning at the camera would serve to reduce the initial file size, so it would download faster, whether the plate-solve is being done at the Pi or crossloaded to the laptop. Downsampling reduces the computational load, but not the initial file size.

Thought I'd figured it all out -- it looked as though switching back and forth between KStars/Ekos running on the Pi and the Mac was putting things in a rotten state, and so long as I only used one or the other at once, I was golden. But now I'm running into connection problems again.

I did find out that if I used an external INDI server instead of running the one internal to KStars/Ekos, I could actually connect the mount directly to the Mac. Not my preferred way to operate, but certainly good to know and it encouraged me to know that the mount wasn't totally on the fritz.

Mojn Peter, check this out: Post your INDI Setup! - Page 4 - INDI Forum - Results from #36

OMG! How does that guy find time to image?! :-o

Wow! Thanks for the link, Keld but my idea to use the adapter and the Pentax lenses points diametral into the other direction. I plan to adapt the ASI to fast and wide lenses to do astroimaging without a mount or guide to keep things simple. For example I plan to take the stuff with me in the next holidays in Greece.

On the long end I also plan to use the setup to tinker chronophotos like these Wings & Things moving in time....! | Flickr in high resolutions.