Hi all, After many years of successfully using a STL-11000M camera, I had the opportunity of purchasing a second STL-11000M (but this time with a FW8-STL). Its serial number is 07081935/C2. I tested it with my FSQ-106N and got…elongated stars. I have been using my FSQ with my first STL camera until a couple of years ago with no elongated stars at all, and with a Canon60Da camera until a few days ago, also with no elongated stars. CCDInspector values of the new camera were so bad, aspect (%) about 50!, and showed a tilt. As weight of STL-FW8 camera is much higher than Canon, I figured out that problem could be in the Camera Angle Adapter of the focuser. I disassembled it and I found that it had almost not perceivable movement. Anyway, I tuned it a bit and get a (very) small improvement, but still with very elongated stars. At this point I talked with the former owner, and he explained to me that he did not remember at all anything about the “Large Format Shim Location and Thickness” document that comes with the cameras, and, what it is worst, that he purchased the FW8-STL later than the camera and made the attachment to the STL without taking care or knowing this “…Make sure any shims (thin washers) that were under the block are put in the same relative position on the FW8-STL. These shims are used to square up the CCD to the telescope optical axis…” … So I am almost sure now that, if there were any shim on the original camera, it was lost during the attachment of FW8-STL. Therefore, that is the first problem. Finally, I made another test with the camera but this time without filter and I get a big improvement (aspect (%) about 25), but still not “perfect”. So the wheel itself may be a second problem. Regarding the wheel problem, next day I go to the observatory I will try to adjust it. If there is any suggestion or guidance, will be very welcome! And regarding the, presumably, non squared sensor. Would it be possible to find out from the serial number, the position and thickness of the original shims? I guess the answer will be no (camera is from 2008…). So, again, any suggestion of how to proceed now (shims, tilt adapter,…), will be most welcome! Jordi PS first image is from my STL camera with FSQ (30 minutes exposure, Ha filter), second is with new camera (20 minutes exposure, Oiii filter), third is new camera (0 minutes exposure, no filter)
We don't have any record of shim data from 2008. You could try using CCDInspector to estimate focal plane tilt, and tweak it out. You can purchase suitable shim washers from McMaster Carr. https://www.mcmaster.com/shims/ring-shims-7/
Thank you for the fast answer, Doug! A last question, what do you think about, for making easy the adjustment, to use instead of shims a tilter adapter, for example like this one: https://www.baader-planetarium.com/en/baader-m68-tilter.html Jordi
It occurs to me that Bill @ SBIG Service & Repair might possibly have some old information that we do not. You might want to contact him at bill at sbig dot com. I've never used one of those adjuster gadgets myself. Note that only a very small adjustment will be necessary to level the camera. The advantage of our shim technique is that it can never slip; the advantage of a gadget like that is easier adjustment. (We measure the tilt using a special machine, so there's no trial-and-error required.)
Thank you, Doug I contacted by PM to Bill and, unfortunately, he does not have this information (By the way, it is fully understandable, we are talking about the year 2008...) I will try to tweak it out with shims. Jordi
Sorry we couldn't help with that, but I'm sure you'll be able to sort it. I don't know what the allowed shim range was for STL cameras, but on modern cameras we don't allow more than 5 thousandths of an inch. If it's more than that then we rebuild the sensor chamber. This gives you an idea of the size of adjustment needed. Here's what I'd hope is a sensible approach. You will probably want to set aside a bright moon night for this. It might be a little tedious: Get a pack of shims, 1 thousandth of an inch thick. McMaster 99040A401 will work and it's 25 per pack so you'll have tons left over. Make a drawing of the front of the camera in a specific known orientation, with a place to write in the number of shims on each screw. Print multiple copies of it. Mark them up as you go. Start with two shims on each of the "top" screws ( both left and right). That will tilt the nosepiece "down". Take images and note effect. Record on the first sheet - shims and effect. Repeat for different orientations, using a new sheet for each step. I'd suggest "Bottom", "Left", and "Right" - but stop if you find you're clearly moving in the right direction. Decide if you need to add more, and how many. If you're close, use 1 shim on each. etc. If you get close in say left/right but it low looks like it's a little off top/bottom, then experiment with tilting in the other direction. This will obviously take a bit of time and patience, but it's going to be by far the best solution once you're done. It doesn't have to be 100% perfect; it just has to be within the focus depth of your instrument, and then you won't be able to see it. Once you have figured it out, throw out all the sheets except the last one. Keep that in a safe place! Obviously this isn't how we do it! But it ought to work with a little patience.
Here's the ShimMap for my STL-11000M, from 2005. I guess the corrections are in inches which would make that 10-thou. Hmmm wonder who the tech DM is?
I would assume David Morrow... That clearly increases the possible tilt to +/- 10 thousandths or more.
Thank you Doug for the suggested procedure, I will try to follow it (on a Moon night ). Thank you also Tim for the information of the shim position and thickness on your camera! It help me a lot as confirm the thickness of the shims in the STL cameras, in my case I have one shim in position B and thickness is also .01". Jordi
Hello everyone, I am writing this just so I can put the "solved" tag on this thread. Although I have ordered and received the shims, I have not used them. The reason is that upon closer inspection, I discovered that the nose piece was not properly screwed to the camera body: there was a gap (measured with a caliper) of 0.32 mm!!! After correcting this problem and installing the camera on my TOA-150 (working at f/7 vs f/5 on the FSQ) I still find a little bit of tilt, but it is really small, and I think I can live with it. Many thanks again to all of you for your help on this issue. Jordi
