RichardNewbie

Thanks everybody. As for cleaning the filter etc, I had already done that but omitted to say so. Apologies. Camera micro-lensing does seem to be the issue. At least it's not the PHQ!

I have been using a new Askar 107PHQ with ASI 7nm NB filters in an ASI filter wheel in front of an ASI1600mm camera, normally running at -4'C very successfully, but have encountered a problem. Very bright stars cause an artifact, see attached, which I cannot eliminate. Is this likely to be the camera, the 'scope or something else? The artifact exists in the original fits files - it is not a processing issue. If it cannot be avoided, what is the best way to minimise/eliminate it. I have gone down to 60s exposures, but the artifact is still there (but IC63 is not). I have tried de-starring (Starnet2), healing the area using Affinity 2, then putting the stars back, but the 'healed' area always shows. Thanks in advance for any and all help. IC63 300s each Ha, Oiii, Sii, 0 gain, 21/1/23. HSO stacked and combined combined using APP.

Further to the suggestion that back focus was an issue, as promised the following was undertaken last night, despite the poor conditions here (Northants). PA to < 1’ each axis. Steeltrack used as variable extension tube. Back focus (using Steeltrack and then C8 focuser to regain focus) altered to get a plate solve FL of 1280.6. See attached. Guiding by PHD2. Max error was 1.5’ each way both RA and Dec, with RMS 0.26 RA 0.23 Dec. FITS header after Astap platesolve attached – it would solve these subs if made mono first, but not otherwise. Shows rotation of 82’, as does the Ekos platesolve. This image of M106 (15x300s subs Altair 183C stacked using Affinity Photo with darks but no flats) shows elongated stars, but to a lesser extent than the previous C8 image of M106. However, the stars are certainly not as good as Same Old Newbie’s image. In the light of the work over the past month at least I can now get half-decent images (if not enlarged). But that is not good enough so I am going to buy a 700mm F7 4” APO triplet – but do not know which one yet. Any suggestions gratefully received! I normally use mono/NB (as with NGC6888 above) and I think a ‘frac would be much easier. The C8 can take pics of the planets. Thanks to all for your input. 2022.04.14_1280FL_Test.txt

I cannot find out if the ZWO EAF (which I have already) can be fitted to a Altair Astro 102 EDT - which I am considering buying. I have tried Altair, Harrisons and the internet - no information. Does anyone know?

OK. I will adjust the spacing such that when focused I get 1280mm FL when plate solving (Ekos does this). I obviously do not have the correct index file for Astap - I only have H18. I will add it to my 'Work in progress'. All I need is a clear night!

Based on the advice given and gratefully received - thank you: Back focus from rear FLR element was about 105mm when the Steeltrack was at mid-position (15mm from min/max position). However, focuser was removed and replaced with extension tubes and back focus to sensor set very close to 105mm from the FLR rear element. Ekos now shows FL as 1250mm after plate-solving. C8 focuser about 17 turns in from extreme a/clockwise position. This will affect the focal elngth? EAF now attached directly to C8 focuser. Collimation screws replaced with home-made thumbscrews, requiring a full re-collimation. Now collimation is slightly better than before (and much easier) and as close to perfect as I am likely to get it (at the image centre). Thumbscrews much better - even if you have to buy them. Home-modified finder scope (50mm Obj, 175mm FL ) used as guide scope replaced with new Altair Astro 60mm/225mm guide scope. I dismantled the HEQ5 Pro RA axis, cleaned and re-greased with the recommended (very expensive) PTFE grease, and reset backlash. RA Axis had become progressively stiffer (‘stiction’) in the past few months– it now swings very freely allowing for much more accurate balancing. Backlash seems a little less than previously. Regret forgot to do a PHD2 mount analysis. Guiding peak error however remains about +/- 1”, with RMS: RA 0.20, Dec 0.16, total 0.26, using PHD2 with the new guide scope FL. Image shift between exposures and star elongation is now much reduced. However, stars still show a little elongation – and these are only 300s exposures. Attached image is M106, 5x300s subs stacked in Affinity Photo, C8 plus 0.63 FLR, ASI183C binned x2. Work in progress: PA. This is done via Ekos as I have no sight of the Pole star – I shall check its accuracy using PHD2. PHD2 mount analysis. I have yet to identify the direction of the elongation. Astap won’t plate solve the C8 images as the FOV is too small. Variation in star elongation at difference exposure times. What made the difference to imaging performance? Your guess is as good a mine! But not there yet..... Comment re SCT from Same Old..... very true. The magnification and light grab of the C8 make it worthwhile trying...

Thank you Never thought of that. I remember that back focus might be an issue when putting a separate focusser in the optical train when I bought the DiamondTrack. I will measure the approximate back focus and make changes - such as removing the FLR or the DiamondTrack. I will update post with results - but it might be some days with the weather forecast! Not quite sure how this would affect the image shift, but your image looks familiar so it's a place to start.

Hi Michael Affinity does not have registration - but I have attached a stack of 16 subs from DSS which does - it has done its best to align the subs. Surely the guiding would have compensated for any PA error - which if the Ekos system is good was very low anyway? I can only presume the trails are RA or DEC guide error - collimation is not perfect but could that would create star trails? Log for the evening of the 23rd when 16 subs shot of M101 using the C8/HEQ5 - my log for that night indicates no other images were taken but a few others may have been. Tks for your interest. PHD2_GuideLog_2022-03-23_204539.txt

Hi Michael – tks for yr reply. In answer to your questions: The image with the long tails is a stack of 5 x 600s subs. I thought SGL would put the verbose file names in the item to show this – but it doesn’t. The single sub is the image with the short tails. The subs were stacked using Affinity Photo – which does not reject bad subs – DSS would probably have stacked nothing as no sub has good stars. As for direction – too complicated for my small brain. Flexure was my first thought – but how could the image shift between each sub? In one session I had image shift for each sub, in the same direction, over 16 subs - that is nearly 2 hrs. Theoretically, if I took 24hrs worth of subs I would get banana-shaped guidescope supports as the guidescope and OTA images became further detached!. Which is absurd. As for guidescope overhang, this is the same one as I use for my ZS73. I attach a 4 x 600s stack of NGC6888 taken with the ZS73 on the same mount with the same guidescope – which shows no problem even if magnified. I am baffled - but thanks for your input.

I have an issue with guiding my C8 which I cannot explain. I have just started using the C8 for deep sky, previously used only for solar system, with my ZS73&HEQ5 Pro used for deep sky – and I have had good results with the ZS73 (FL=460mm). Not with the C8. PHD2 (running via Ekos) shows a guiding accuracy of around 1” RA and less on Dec with either scope. That is to say the errors peak around +/- 1” on the PHD2 chart. Oddly, Ekos shows the accuracy as a bit lower on the chart displayed under the guiding tab, but that is another matter. The C8 images (600s, M101) show small star trails (see pic). These become large when the images are stacked (see pic). PHD2 shows no error messages, and seems to be tracking the same star - I have sat and watched over several exposures. The length of the trails can vary a bit between images. What could be causing the consistent tracking failure? If it was just poor tracking surely the stars would be blobs not trails and PHD2 would report much greater error? I have discounted mirror shift as the problem affects all images, roughly the same. Also, M101 is near the NCP and the meridian here. As a control I have shot and stacked 5s images which individually look OK (but for very bad S/N ratio) but show the trailing if 50 stacked. Any suggestions would be much appreciated. The setup is as follows: C8 with FLR (FL=1300mm) on HEQ5 Pro with Rowan belts (correctly tightened), Dec backlash eliminated, RA backlash nearly eliminated – but as good as I can get – any tighter and PHD2 reports unable to move the mount. Load around 10kgs excl counterweights. RA set slightly ‘east heavy’, Dec balanced. Clutches set as tight as possible. Pulse guiding. Guide scope 50mm/176mm FL mounted forward on ADM-type bar across top of C8 using normal small dovetail, the scope held in rings fore and aft. No noticeable flexure in guidescope mounting. Guide camera QHY5L II (1280x960). Attached to C8 are 0.63 FLR, then Baader DiamondTrack with ZWO EAF, and finally ZWO ASI385. Guiding via PHD2 on Raspberry Pi via Ekos. Pi also runs INDI server for the mount, cameras, focuser, reporting to Kstars 3.5.8 on W10 remote PC via 1gb Ethernet. Polar alignment (using Ekos) < 30” RA & Dec.

The solution! It was the mount - a 10 month old HEQ5 with only a few hours use. I fitted a Rowan belt system and now get sub 1" range on Dec and RA using PHD2. I think the main problems were the RA backlash was very large and the RA worm drive end float nut was screwed up very tight - both were sorted when the Rowan system was fitted. I also dismantled the mount and renewed the grease in the Dec and RA worm drives. Oddly, the was no grease on the HEQ5 spur gears.

Thanks everybody. Regret that none of the suggestions have worked. Recalibration has been done regularly each night as I switch from Ekos to PHD2 and back again, and change target object. I guess there is something in my setup that is causing the problem. I will persevere the next clear night. I will post again if I find a solution.

Tks for this. Correct - my version is actually 3.5.4 as well. I will try these ideas the next clear night. I do guide using Eqmod - only used ST4 to see if it made any difference. It didn't.

Hi Star Gazers. I hope someone may be able to help me. For my full setup see end of post. After some successful tests of guiding in the last month as I progress toward doing DSO imaging, it has just gone pear-shaped. I have been using Ekos internal guiding, pulse not ST4 using a QHY5L II camera. In the past week the guiding process cannot keep within 2.5" for more than a minute, and within a couple it can be 40" out - RA is the main the problem. It does not always happen – just mostly. In desperation, to avoid moving the guide camera, etc to another PC, I started using PHD2 on the Pi itself (after ‘disconnecting’ the camera from Kstars and ‘connecting’ to PHD2). It works OK and the results are quite good - same INDI server, same guide scope, camera, mount - literally just changing from Ekos to Pi-based PHD2 within minutes solved the problem. When I set guiding on Ekos the next night, it again failed. I leave the mount connected to Ekos, but obviously not the camera. I have tried another camera (ASI385) and using ST4 – no better. I have checked that cables are not snagged, clutches are tight, and scopes are balanced and secure. Polar alignment is within 60” each time (as shown by Ekos Legacy PA function). Obviously I can continue to use PHD2 on the Pi, but I would prefer the Ekos internal guiding system for unattended imaging (eventually!). I attach a snip of the guiding screen when I had another try last night. Hope all this is clear.... Setup: HEQ5 Pro mount (10 months old) Serial/usb adapter INDI server running on Pi 4 8GB under Astroberry. QHY 5L II guide camera. Cheap 50mm finder scope as guide scope. Kstars 3.3.4 desktop under W10 remotely Ethernet connections to all Mount (as Eqmod) and guide camera on INDI running on the Pi .