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almcl

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About almcl

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    Telford, Shropshire
  1. Afraid I don't know enough about your particular camera, but for my Canon 200 mm lens I use a home made Bahtinov mask and live view or connect to a tablet or laptop and focus using that. The free version of APT (Astrophotography Tool) has some built in focusing aids, if that will work with a Nikon?
  2. I had something similar on my Canon 700d a few years back. On advice from the camera supplier, (Juan Fierros - www.cheapastrophotography.com) I disabled live view and the problem went away.
  3. I hope your replacement guidescope solves the problem, but if it doesn't, you might find that getting rid of the scope rings with their plastic tipped screws and clamping the guidescope firmly to the dovetail with, for example, clamshell clamps and then clamping the dovetail to both the main scope's rings will help reduce the mechanical flexure. There are several occasions in your guide logs where the DEC performance is actually better than the RA - I haven't looked at all the logs, but here's one example: When the Dec goes wrong, it's large (the largest peak below is almost 20 arc seconds) and pretty rapid and, as the DEC motor was not running, not down to software. Here's an example: There is still some backlash (it takes 15 pulses before the small deviation at 00:53 comes back within limits, for example) but this doesn't seem to be the main problem.
  4. I see your point, but like you, I am not sure if the distance at which the secondary (which is flat) intercepts the light cone is significant? Anyway, with a slightly different collimation and a change of connector to the focuser, last night's 'quick 'n dirty' (pre-nautical dark) shots were a lot sharper and the field a lot flatter: What I should have done, of course, was to rotate the camera through 90° and compare the results. I may be blaming the scope for something that is camera caused. Next clear night, I'll give that a go.
  5. Thanks for the thoughts. I believe that the corrector to main mirror distance is important but it seems pretty fixed; the corrector is nailed pretty solidly to one end of the OTA and the mirror cell is fixed at the other end. I have had another go at collimation, although I can't believe it would make so much difference. My APS C sized sensor gave this result for curve/tilt: but this for FWHM: the scores were 61.4 for curvature, 37.0 for tilt and 8.65% for collimation. Not sure what the first two figures mean though.
  6. Apologies in advance, this is going to be image heavy. So after only two days the newly arrived SW 190 Maksutov Newtonian got to see some stars! First, after two days of fiddling with the collimation, here's a star test: The next step was a Bahtinov mask check. I didn't notice till afterwards that while the bright star (which was centre frame) appears in focus, the little one to the left is clearly not. Not sure if this is tilt? Or something else? Went looking for a star field and happened on Albireo. Again didn't notice the reflections till afterwards. My Canon 700d was connected directly to the scope, no filters, no coma corrector (obviously!) so not sure where this red reflection is coming from and does its slightly offset position suggest that we haven't quite nailed Collimation? The slightly more worrying aspect is the view of a small star cluster (single 20 sec image at ISO800): In case it's not clear, here are full size crops from the corners: top left bottom left bottom right top right centre This looks like quite bad coma to me. I ran the image through Maxpilote to get a sense of where the error might lie and the results suggest that while the centre of the field looks OK, the right and left edges and corners are a different matter, suffering badly from curvature, lack of focus and tilt. Not sure how much faith to put in these figures but is this what one should expect from a Mak-Newt? One of the claims made for this model on the Optical Vision Website is: " Stars appear as classic pinpoints across the entire field. Perfectly optimised for modern DSLR cameras. " Clearly this isn't the case here, but could this be operator error causing camera tilt? I'd really welcome fellow SGLr's views. If anyone would care to run the single image through alternative software, there are .fits, .cr2 and .tiff versions here: https://www.dropbox.com/sh/eq2wub9q49rdpv8/AABnoazj6OQALRWRkq8SEa2ya?dl=0
  7. The postman delivered my brand new SW 190 MN today, several days earlier than expected. Yippee! Great fun unpacking and looking at it, but with no prospect of clear skies I put it on the bench to check collimation. First with a Concenter then with a Cheshire. Both indicated that collocation was 'off', but by completely different amounts. I had hoped that the reportedly more robust collimation of the Mak Newt would have survived the trip from the factory, but alas it was not so. I've never really trusted the Concenter, which appear to ignore Newtonian offset and so proceeded to align with the Cheshire. The secondary reflection was round, but the primary spot and reflection of the eyepiece hole were not in the centre. Now I am no stranger to collimating Newtonians and believe I am reasonably OK at it, so I settled down to line things up. It didn't take long to get the primary spot and Cheshire eye hole lined up with the crosswires in the centre but on this MN there is also a ring marking the centre of the secondary and this is absolutely resisting my efforts to bring it into the centre. The diagram below indicates the situation, the magenta ring being the recalcitrant secondary centre mark and the orange lines the copper cross hairs. I am guessing that the secondary needs moving away from the corrector plate, but am a bit reluctant to try this as I have read that this distance is accurately set at the factory and shouldn't be altered? If any 190 MN owners who have faced this and solved it would care to share, I'd be very grateful?
  8. If you want really cheap, a second hand web cam with the lens removed can be made to work. I started off guiding with a Logitech C250 on special offer £15. It worked but couldn't always find a guide star. After a few months it was replaced first by a QHY5l ii mono and when the USB socket on that broke , by an ASI 120 mini mono which I still have.
  9. As Paul says that's a huge swathe of sky (40 x 28 degrees) and you have actually captured the Triangulum Galaxy (M 33) as well. You seem to have a bit of light pollution and quite a lot of noise. If you can take multiple images and stack them, together with some calibration frames, you may well be able to get some more detail and reduce the noise. But if that's your first try, well done: you have got the Andromeda galaxy almost dead centre. It's just a matter of learning the techniques now. Here's a link to your image solved in Astrometry.net: link
  10. A slightly cheaper alternative is to fit the Lacerta dual speed upgrade kit. Took me about 10 minutes to fit; the fitting instructions (which are very good) probably took slightly longer to absorb.
  11. The image shows up the optical imperfections of the ST80. It suffers chromatic aberration (coloured fringes around stars) and also coma. The focuser sags when a heavy camera is attached which makes the problems worse. I never used it for visual as it came (secondhand) without a diagonal and without one the viewing angle would have been very awkward. The colours are approximately correct although the yellows are missing as a consequence of having to imge through a light pollution feature.
  12. Welcome to Stargazers! I started out in much the same way, an EQ5 and a 200p. I added motors and then got one of Juan's (https://www.cheapastrophotography.com/) astro modified Canon cameras. I chose a 700D with the flip screen but the screen became redundant when using a tablet with DSLR controller and even more so with Astro Photography Tool (APT) as the camera controller. You may be told that you won't be able to focus a DSLR with the 200p and that astro modding will make the camera useless for daytime photography. Neither of these are true in my experience and Juan gives a good demo of this on his website. Along the way I did change to stepper motors on the EQ5 and then eventually upgraded the mount, added a coma corrector, some filters, tried different guiding arrangements (presently using a Canon specific OAG and an ASI 120 mini) and lots of other little tweaks and mods. If you are on a budget a secondhand low shutter count Canon which can be modded later might be a way in?
  13. +1 for Wimvb's point. Here's an example using your screen grab:
  14. I have had something similar happen a few times with the later version of DSS (I used 4.24 Beta 4 here) and it seems to be down to star selection. I notice depsite raising the star threshold to 80% that DSS reports it is using over 4000 stars when doing the final 'align channels' so perhaps it is aligning on noise perhaps introduced by the bias or flat frames? I wonder if @perdrix has an insight into this?
  15. Here's an image of the Heart nebula shot with an ST80 and a Canon 700d about 5 years ago. Processed in DSS and StarTools. 18 x 180 sec lights, 30 flats and 30 bias frames. I acquired the ST 80 as a guide scope and wanted to see how it performed as an imager. I haven't used it for imaging since.
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