Merlin66

Vlaiv, Glad you found that error.... I think you need to revisit Suiter's "Star Testing Astronomical Telescopes". On p61 he models a simplistic analysis of the Airy Disk based on the Heisenberg uncertainty principle and comes up with an answer close to the 1.22lambda/D. I have yet to see an astronomical image showing the Airy Disk. (On the bench a pinhole optical system is usually used to generate the Airy disk images normal see in the text.) It needs at least a >f30 system and absolutely perfect conditions. Suiter's work is based on VISUAL and high magnifications. What we record is the PSF of the seeing disk. Re Sampling (See Suiter, p41) and the MTF Chapter 3.4. Eversberg and Vollmann in their "Spectroscopic Instrumentation" p 76 discuss at some length the issues of effective sampling - starting with the Nyquist criterion - they advocate at least a sampling rate of >3. (This again is based on the PSF rather than the "absolute" Airy Disk) I'd also refer you to Schroeder's "Astronomical Optics".

Mike, I agree 100%! I have the one volume edition. The other ol' favourite would be Chamber's "Astronomy" - 1867

The typical bandwidth of a single stack etalon is 0.7 to 1.0A - this is sufficient to show all the major solar features, the wider bandwidth is sometimes better at showing the proms due to their Doppler shift. A double stack gets down to around 0.5A and this enhances the surface details and may require some "extra" tuning to maximise the views of the proms. You can double stack external tilt etalons - I used a double stack SM60 pair for many years on the ED80. (Adding a double stack filter to a poorly performing single stack etalon will slightly improve things but consider the cost v's benefit)

Not much changed since the 2012 set-up.... The Baader wedge has been "adapted" to just a ND1.6 configuration (temporarily) to allow the Omega CaK filter stack to be tested. The 100mm Spectroheliograph is semi-operational - the weather has significantly reduced the opportunities to do final testing....

Do you think there are enough users who have a basic Star Analyser grating (or other spectrograph) to justify a spectroscopic challenge for them??

+1 for a Spectroscopy challenge! When/ if you get serious I can assist.................

Ahhhh I'm glad Peter corrected me! I assumed looking at the Black box that is was a Stage 1 mod.

Gina, As part of the mod it should have already been set up to the correct position. The focusing on the solar disk is by using the focus knob on the Black body of the PST. The tuning ring is used to fine tune the H alpha wavelength to show the solar detail.

As said Gina, there's no real need to consider a focuser on the scope...

Interesting, I picked up an excellent 4" CARTON objective for my spectroheliograph.........

Gina, You don't have to worry about or consider any focusing of the donor scope. The etalon NEVER moves relative to the donor after initial set-up. It's always -200mm from the prime focus. Think about the donor just as a fixed replacement for the original gold tube in the PST. Final focusing is always achieved behind the etalon - I use a Borg helical focuser on my PST Mod.

I use the QHY5ii and the Lodestar for spectroscope guiding - which is very similar to OAG. This is on my C11 at f10. No issues so far, either in finding a star or guiding. Practise........

Yes, the tilter sits immediately in front of the ASI 174. Normally you'll need around 1000 frames per exposure - this allows AS! to select the best frames for subsequent stacking, then apply Registax wavelets to bring up the image.

Why the x2 Barlow??? I use the ASI 174MM but need a tilter (1.6 degree) to suppress the Newton Rings.

Spill, with my semi remote set-up with the 60mm electronic finder on the C11 at f10, I can center the finder on a target star and have it sitting on the 20micron slit gap in the spectroscope. certainly accurate enough for plate solving......

I only do spectroscopy so the "imaging" camera only sees spectra not the sky. The built-in guider on the spectroscope has a small field of view ( the C11 at f10) and can generate "double star" images of brighter field stars. Not suitable for plate solving. My solution is to use a DMK51 camera on the 60mm finder as an electronic finder and use these images for plate solving. Hope this helps.

OK I'm back home now..... Connecting my EQ6Pro mount with CdC and EQMod and double checking the ASCOM settings for my camera - I use AstroArt, then configuring ASPS for the focal length/ pixel size of my electronic finder I can obtain a fits image, solve and sync the mount.... Note the "Alignment/ Sync" options in EQMod Tools. Click the small notepad icon and then tick all the sync options.... Works for me. If you upload (or send me) a typical image which you're trying to solve , maybe we can move forward. Ken

OK I should be able to access my computer later today. I'll verify all the settings I use in Eqmod, CDC and ASPS. can you confirm that the camera you are using definitely provides a workable image under your ASCOM settings. If you can upload an example I can run it through the process.

this might help......

Hmmm, not with my computer at the moment, but a couple of things come to mind. you can give the file and location anything you want. unpark the mount to allow for re-syncing. Tick the ignore option to minimize any conflict and double check the focal length and pixel size. it should then work IF the camera with the same ASCOM settings shows a reasonable working image with the selected exposure I.e. Enough star images to be identified. try the camera independently first.......

Hmmmm which camera and scope were you using to obtain the reference images?? were you obtaining sufficient star images for identification? what error messages (if any) do you see???

Looks OK.... what camera were you using??? To get best results you need a mono fast frame camera like the ASI 174 or similar. You can then acquire an AVI of a few hundred frames and use those to provide a detailed image with software like Registax.

Just fit a bit of Baader film over the finder and just use that?? That's what I do.......

Yeah but, It's only one of the polarising elements you need (half of the assembly you show)....rotate the filter/ eyepiece/ camera to see if the reflections are being reduced.

You coupon could try a polarizing filter in front of the camera. This may suppress the unwanted reflections. Seems to work well with some PST mods.