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BrendanC

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Everything posted by BrendanC

  1. Hi all, I recently decided to take the plunge into mono, after two fun years with my trusty EOS1000D and 130PDS combo. So, I've recently invested in a (second-hand) ASI1600 MM Cooled with 8-position electronic filter wheel and LRGBHSO filters. Everything seems to be hooked up and working fine, and I can achieve focus. However, in order to do so, I'm noticing that, to my slight dismay, the focuser tube is actually further in than it was with the DSLR, and intrudes on the primary mirror even more. I did not expect this. I think it's because of the combination of camera plus EFW plus 0.9x coma corrector. I think the backfocus is correct because my understanding is, if this wasn't right, I wouldn't be able to achieve focus at all. Am I right? I've looked into removing the coma corrector from the chain, and it seems essential. So, my options are: Live with it - which I might be able to do, don't know yet Move the primary up the tube - which I'd rather not do Chop the focuser tube - which I'd really not rather do Get a different scope or camera - ditto Any takers? Thanks, Brendan
  2. OK, thanks anyway. Looks like I'll live with it when shooting very bright stars, and/or fix it in post processing.
  3. Very comprehensive answer, thank you! I've collimated the heck out of this thing with a Concenter and Cheshire, so I'm glad that at least that's not the cause. What would the fix be though? Would perhaps painting around the edge of the secondary make a difference? I've flocked opposite the secondary, and painted over the bright bits I can see such as screwheads, so if painting around the primary might help, where it's silvered, then I might give that a go. I just worry about doing irreversible things to it. If this is only going to affect unusually bright stars however, then I might leave it.
  4. Hi all, Here's my latest shot - IC 1318 - with one huge diff spike off Sadr. What causes this? Is the secondary not quite aligned properly?
  5. I want a method to determine the rotation of my camera, for a given DSO, before I even start plate solving, so that I can get closer to the actual rotation needed, and spend less time actually outside plate solving. I knew it was going to be difficult to explain this! While planning, if I frame an object in Stellarium, I don't know for sure what, for example, 35 degrees rotation means I need to rotate my camera by - or, even, if this is consistent given the position of the object in the sky at a given time.
  6. Not sure I'm explaining myself very well here. What I'm trying to do is in fact increase the time I spend imaging, as you say, by getting my camera closer to the proper orientation before I even go outside with the scope. That way, I spend less time shooting, plate solving, rotating, repeating. It's not just for theoretical interest. I wouldn't benefit from plate solving old images, because I wouldn't know how the camera was oriented when I took them. I'll just do as I said, align the camera with the scope, take some pics in various parts of the sky, plate solve them, see what the rotation figures say.
  7. It's actually a Google Sheet - I'll PM you.
  8. If you could do this, and make it work reliably, it could be incredibly handy.
  9. Thanks! It's a very kind offer, and if your Python prog could do this for my lat/long, for a year (or more!), outputting a nice CSV or similar format, I'd definitely be up for it. Only if you'd be doing this for your own amusement (which is kind of what I'm doing with this spreadsheet, truth be told). Ideally it would also do the Moon's RA, Dec, culmination, height at culmination and phase, but I realise that's pushing it...!
  10. Thanks. I've been playing around with that other data. It's in a decidedly unfriendly format for actually doing anything with it, but I'm definitely considering it.
  11. Hmmm, interesting, and it could be all copied and pasted very quickly, but that big, square layout would take a radical rewrite of my spreadsheet to read that format. Thanks anyway, it's a definite contender.
  12. I noticed that too, but I'd rather not have to get into APIs etc, and certainly not for $99 per year!
  13. But it's still displaying incorrect times though, right? For example, it says the Moon rose at 20:44 on 20 Feb. It didn't. It rose at 22:03. On the previous day, the 19th, it rose at 20:44. So it's a day out. (These are local times to me btw, I don't actually live in London, but you might see the same anomalies if you specify your location).
  14. Hi all, I have a spreadsheet that I use to help me plan my shoots. To plan around the Moon, I've been using data from this site, because it very conveniently allows me to download the output as a CSV file which is easy to import into Excel: https://in-the-sky.org/ephemeris.php?startday=31&startmonth=12&startyear=2021&ird=1&irs=1&ima=0&iph=1&ias=0&iss=0&iob=0&ide=0&ids=0&interval=1&tz=0&format=html&rows=25&objtype=1&objpl=Moon&objtxt=the%2BMoon&town=2643743 However, I just realised: it's wrong. On days when there's no moonrise or set, for example 7 Feb or indeed tonight (22 Feb, which is how I just spotted this), it seems to get confused, with the times offset by a day before or after - I've checked it against several other sources. It sort of seems to get back into sync somehow, but basically, it's wrong. I had a similar problem when using this site to locate a comet a while ago, emailed the guy who runs it, got no response. I've emailed him again about this, but I don't expect a response this time either. I've tried building in clever functions to my spreadsheet that recognise this and skip a day or go back a day, but I think there are other strange, random issues with the data besides this. So I need an alternative source. Previously, I used this site, but it's a pain to have to copy the table, paste it, extract the data, etc: https://www.timeanddate.com/moon/uk/london OK, maybe a couple of hours or thereabouts, but still a pain. And I'm lazy. It also doesn't have the Moon's RA and Dec which I also find handy, to calculate how close a given DSO in my target list will be to it. So I was wondering if anyone else knew of any other sites that actually show the correct data, and that have a download feature? Thanks, Brendan
  15. Thanks @iapa, I think I'm in agreement. The geometry is fairly mind-bending, and I think you're right that really it's down just to plate solving and getting it right in the field. The real reason I ask is that I'm building a funky spreadsheet that helps with planning, and it just occurred to me that this might be another nice feature of it, ie so that I could type in the rotation according to Stellarium, and it would just tell me how the camera should look - just to get it close-ish to the right rotation, and make the final tweaks with plate solving a bit quicker. But I'm thinking the theory won't fit the practice. I'm still going to take some shots with the camera at neutral, panning across the sky, solving and then noting the rotation, and it might proving interesting, who knows?
  16. Sure, I can do the same (kind of) in APT - shoot, plate solve, it tells me the degrees I'm out by, rotate, iterate. What I'm trying to do is work out how much I should rotate the camera before I go outside! I really like using Stellarium to plan the framing and timing, so, let's say I want to do M42, and I find that, according to Stellarium, the best framing for that is to rotate the frame by 90 degrees. Now, given that my camera is usually in its nice 'neutral' position so that it's aligned with the scope, is it possible to convert the Stellarium rotation into camera rotation? That is, if Stellarium says 90 degrees, by how much from the neutral position do I rotate my camera? Or, to put it another way, how should I rotate my camera on my scope so that it's at zero degrees when I take a shot? That might be an easier way to express this actually. My instinct tells me it should be a simple case of taking shots in the neutral position, at several different spots in the sky, and if they all agree then I'm right in that there is a constant conversion factor and it should be fairly easy. But as with so many things in this game, I'm also prepared to believe that it isn't easy! I'd also rather not waste time having to take shots and figure this out myself. So, I just wondered if someone could, you know, just tell me!
  17. Hi all, Not really sure how to express this, but I'll try. I'd like to be able to get my camera roughly in the right orientation before a shoot, so that if, for example, I need the frame to be rotated at 75 degrees to frame an object nicely according to Stellarium, I can get the camera somewhere near that before I start. Then I can just take a shot, plate solve, rotate the camera, iterate until we're all set. I have a nice 'flat' position for my camera in which it's aligned along the scope ie so that the top/bottom longer edges of the camera are aligned with the scope lengthways (a Newtonian - which makes this more complicated, in my mind, on an equatorial mount). In fact, you can see that position in my avatar, I just realised. I've been trying to get shots, and then plate solve them, to find out what this flat position actually equals in terms of degrees rotation according to the equatorial grid. Then it should be a simple calculation to say 'this is your flat position on the scope, which equals X degrees in the sky, so to rotate it to Y degrees, just rotate it Z degrees on the scope'. However, I've not had enough nights to do this recently, and I'm lazy, so I thought what the hey, perhaps someone can tell me whether this is possible on the SG forum! Before I waste time, effort and tears on trying to work out something that seems to be easy but turns out to be hard/impossible. I'm assuming it would be a consistent rotation conversion no matter where the camera is pointing? Or, does it depend on where in the sky I'm pointing and/or where on the planet I am? If so, does anyone happen actually to know what the rotation conversion might be? As in, has anyone done this before? Am I making any sense here? Thanks, Brendan
  18. Thank you so much - this post has really inspired me. I honestly hadn't really thought about it from that perspective.
  19. Well now, the thing is, I used to live in London. Then I moved out to the country, about 12 years ago. And, when I retire in a year or so, I'm planning on moving back to London! Because I've had enough time now to realise that. given the choice between culture and nature, for me, it's culture. So, I want the choice of visiting a world-class art gallery/museum/library etc, in the greatest city in the world, for free, even if it means something has to 'give', which is looking like it's going to be the astro, at least in its current form.
  20. Ah, well, I've done plenty of camping in the past! In fact I used my old tent as a scope cover until I realised the constant UV had weathered it and it basically fell apart. Will definitely get in touch if/when the time comes. Thanks!
  21. Already seen your images and they're really great. I will most definitely contact you if I have more questions, thank you very much for the kind offer. It does look like it might have to be fully commit to mono with filters, or consider just solar system, or maybe look into a means of getting out of London on clear nights with maybe a lighter setup. Or, give up.
  22. Thank you both. Btw, @carastro, I just checked out your profile on the forum to look at your photos, and noticed you were viewing this topic! So, if you have any advice, that would be very much appreciated.
  23. Hi all, I've been loving astrophotography for the past two years, having moved from an AltAz mount with 130P scope, to guided NEQ6 with 130PDS and modded DSLR, recently started doing a bit of HaRGB too. Mostly DSO - nebulae, galaxies, clusters, but with occasional forays into solar system stuff. However, I may be moving from my nice Bortle 4 skies to London. I'm hoping this doesn't mean the end of my new-found hobby/obsession/passion/interest. I'd be keen on staying in the OSC camp, simply because mono plus narrowband filters is very expensive and fiddlesome, from what I can see. It's two steps forward whereas I'd rather just take one. I don't think the DSLR will hack it, so I'm considering upgrading to a cooled astrocam, probably something based on the 294 chip such as the Hypercam 294C Pro Tec, with a dualband filter such as the L-Extreme. That's the plan anyway. But there are nagging doubts. Mainly: Am I on a hiding to nothing trying to do anything decent in London? If it is possible, then would OSC with dualband work out, or is mono with narrowband the only way to go? Finally, is it worth buying secondhand to make the pounds go further, or should I buy new, and get all the lovely warranties that come with it? Everything else I've bought is second-hand but the camera plus filter would be my most expensive purchase yet and I worry about getting something that dies on me after spending hundreds of pounds on it. I keep going around these questions in my head and I need some external input! Any/all comments welcome. Thanks, Brendan
  24. Interestingly it's the 294 chip that I've decided to look into and the Altair is on the shortlist so thanks for this.
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