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almcl

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Everything posted by almcl

  1. 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.
  2. 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.
  3. 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
  4. 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?
  5. 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.
  6. 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
  7. 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.
  8. 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.
  9. 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?
  10. +1 for Wimvb's point. Here's an example using your screen grab:
  11. 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?
  12. 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.
  13. I had a similar problem to solve when starting to use my EQ5 with a home-made camera-and-guidescope mounting plate. Calculating was way beyond my theoretical abilities so instead I set everything up and hung bags of dried goods from the larder from the middle of the counterweight bar until I got a good balance. It turned out I needed about 2 kg and fortunately Bresser did a a 2kg weight with the right centre hole diameter. There's one on Ebay at the moment but at £40+ it seems a little expensive for a chunk of white painted steel?
  14. Could be, but now I look at the time stamp it was a little after 3.00. Never realised the early morning sky was so busy! Night jet ban, what night jet ban?
  15. My effort from Sunday morning. I was a bit annoyed at the contrail initially and even more so by the out-of-focus clothes line (perils of back garden astrophotography) but at just before 3.00 am it was a nice visual sight. Canon 200 mm lens, 1 sec @ ISO 800
  16. Polaris is the brightest one there abouts, having said which I managed to choose completely the wrong one at a dark sky site - too many 'bright' ones! One thing I find makes it a bit easier is to set up quite soon after sunset - before the end of civil twilight, if possible - fewer stars are visible so making a mistake is less likely. Using the polar scope on EQ5 or AltAzEQ6 I can usually get within 10' (as confirmed by PHD2 guiding assistant) and on lucky occasions within 5, but this only matters for imaging. For visual 'near enough is good enough'. To this end marking the spots where the tripod legs go can help. I sunk some small paving blocks in the grass, made a small dimple for the north leg and now Polaris is always in the polar scope field on initial set up. There are a variety of apps if you are imaging, Sharpcap 2.9 is free and has a polar alignment routine, PHD2 (also free) has no less than 3 and none of these 4 agree with each other, which makes one wonder how exact a science Polar Alignment is?
  17. almcl

    clip from 6.mp4

    From the album: wild life

  18. almcl

    wild life

  19. almcl

    clip from8

    From the album: wild life

  20. Thanks both. In truth, although I had read about them in Sky at Night mag, I thought my northerly and north westerly horizons were too tree obstructed for them to be visible. Nice to find they aren't!
  21. Last night, just as I switched off the PC and was preparing for bed around 11.00 pm, I noticed that the sky was clear (unforecast!) and that there was a noctilucent cloud display. Quickly attempted to set up my Canon 700 with its kit lens and snapped off a few shots at this, new-to-me, phenomenon, not really expecting to get very much. In truth most of the shots suffered from camera shake, out of focus, under or over exposure or a combination, but this one isn't quite as bad as the rest: Did anybody else see this?
  22. My experience matches Tooth_dr's. Been using my ASI 120 mini with an OAG for two and half years now and it has never failed to find guide stars.
  23. + one for a 13.8 volt supply. I use this one, rated at 15 amps and it runs my Alt Az EQ6, camera (via a buck converter), camera cooler, dew heaters (when required) and USB hub with hardly any voltage drop. Something similar must be available in the USA?
  24. Yes. As shown here https://www.mathopenref.com/ellipseaxes.html Yes, move the secondary away from the focusser by the specified (small) amount towards the opposite side of the OTA. This is to ensure that the secondary catches the whole of the light cone from the primary mirror. No, don't move it towards the primary, that will defeat the object.
  25. I've been using the same 32 Gb Transcend card in my astro modified Canon 700d for five years now. Never got remotely close to filling it, taking both raw and jpg images, even when I took flats and bias along with the lights every night.
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