BrendanC

I'll take that as a massive compliment, thank you.

Hi all, I recently discovered that I live very close to where an eminent astronomer used to live, called William Rutter Dawes. If the surname's familiar, that's because he is the originator of the Dawes Limit, used to determine the practical limit on resolving power for a telescope. He also has a crater named after him on the Moon, also one of Saturn's rings, and received the RSA Gold Medal in 1855. So, quite a significant figure! I was intrigued when I discovered that the telescope that he had in his observatory (the hole through which it poked is still visible in aerial shots of the house) is still in use at Cambridge University. So, I attended one of their night-time lectures and by special permission, was able to see the scope and take some snaps. It's called the Thorrowgood scope and you can read more about it here: https://www.ast.cam.ac.uk/about/thorrowgood.telescope And here are some of the shots I took! Given that my house dates back to 1695 I think it's a virtual certainty that Dawes must have at least walked past it on many occasions, and who knows, might even have been in it! And here I am, 150 years later, practising astronomy (in my own small way) about a minute's walk away. Just thought you might find this of interest. I find it quite inspiring! Cheers, Brendan

Thanks! One of the benefits of a Newt with those diffraction spikes.

Hi all, Pleased that I managed to get enough data between the clouds and before astro darkness for this one! • 4:22 hours of integration at ISO800 from 43x240s + 30x180s subs • Bortle 4 sky, no Moon • Calibration: 25 flats, 25 dark flats, 50 darks • Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher NEQ6 mount, Canon EOS1000D DSLR camera with IR filter removed, Sky-Watcher 0.9x coma corrector, Datyson T7C guide camera, Angel Eyes 50mm guide scope • Software: polar alignment with SharpCap Pro, guiding with PHD2, capture with Astrophotography Tool (APT), stacking with Deep Sky Stacker (DSS), post-processing with StarTools, Photoshop CS2, Affinity Photo and Topaz Denoise AI

Thanks! When I say DSLR I mean with a telescope attached, obvs.

Hi all, Not posted an image in this part of the forum before, so here goes...! Two versions, one 2x2 binned and one unbinned - I like to do this with shots that have a relatively small central object to get an idea of the object and its surroundings too. Details are: • 5:08 hours of integration at ISO800 from 224x60s + 21x240s subs • Bortle 4 sky, Moon at average 36% phase, 44° height • Calibration: 25 flats, 25 dark flats, 50 darks • Hardware: Sky-Watcher 130PDS scope (F5), Sky-Watcher NEQ6 mount, Canon EOS1000D DSLR camera with IR filter removed, Sky-Watcher 0.9x coma corrector, Datyson T7C guide camera, Angel Eyes 50mm guide scope • Software: polar alignment with SharpCap Pro, guiding with PHD2, capture with Astrophotography Tool (APT), stacking with Deep Sky Stacker (DSS), post-processing with StarTools, Photoshop CS2, Affinity Photo and Topaz Denoise AI Thanks! Brendan

Seeing the Moon for the first time through a telescope is better than seeing the Moon for the second time through a telescope!

I'm also based in Bucks! Welcome.

You're right - I'm not that bothered...

I really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really, really want to see this: https://www.thehuntforplanetb.com/ If this other doc of his is anything to go by, it'll be great: https://www.youtube.com/watch?v=FLD9LKq0u9E However, despite there being several reviews of it online, and even asking about this on their Facebook page and on Twitter, I cannot find it anywhere online to stream/watch/download/buy/whatever. Does anyone know anything about availability or release date in the UK?

Thanks, I'll give it another go if you think it'll work, but I've never been able to get anything decent out of it! I'm just wondering whether I'm correct about losing data if I use the Kappa Sigma stacking method. I think the maths is such that I would lose data, and I've seen people use layers and masks instead. If I'm wrong about losing data then I'll carry on as before. Thanks for responding.

I know this question has been asked quite a lot, but as I say, I haven't seen anyone cover the issue of whether data would be LOST using this method!

I've been thinking a lot about stacking in DSS recently. Here's one of those thoughts. Say I have 100 exposures of a galaxy at 60s, and another 100 at 240s. I know that I could stack them all in one go in DSS, assuming I correctly allocate the calibration frames etc. I also know that this would improve the SNR. But, in doing so, how would the maths work for the fainter stuff in the 240s exposures? I have a sneaking feeling it would average it out from what it can see in the 60s exposures. I tend use to use Media Kappa Sigma for my lights, and I know that there's an algorithm that's supposed to be ideal for this, called Entropy Weighted Average, but I've tried that without much success. The alternative approach is to stack them separately then combine in Photoshop using masks and layers. But then, I wouldn't benefit from the improvement in SNR that way. The noise would just be greater in each stack. So what's the best way to do this? Is it, as is always the case, 'it depends'? I've been through lots of posts about this, both here and elsewhere, and I don't see anyone addressing the issue of potentially losing data from the 240s exposures by stacking them with the 60s exposures. Thanks, Brendan

Cheapskate.

It's a Präzisionsokularauszug with an Okularauszug included. £1,143 per syllable.

0.62p per square mm. Bargain!

And Swarovski. Don't forget the Swarovski.

Yep, you've got me bang to rights on that one. I know nothing about Takahashis. In fairness I did say very roughly, in the same semantic sense that an elephant is very roughly a hippopotamus. Anyway, as I said, I wasn't being entirely serious. But I do still think, even with all the fancypants optics and your hyperbolic wosnames and your correcting widgets, it's an eye-watering amount to pay for what really does amount to two mirrors.

I was idly browsing just now and wondered to myself: "Does Takahashi do Newtonians?" As you do. They do. And the very rough equivalent of my trusty Sky-Watcher 130PDS, currently retailing at £229, is this. For £2,398: https://www.firstlightoptics.com/telescopes-in-stock/takahashi-epsilon-130-ed-f3-3-newtonian-astrograph-reflector.html Now that seems a lot of money to pay for what is essentially two mirrors! A bit of maths-related fun: it seems to me that the primary is the same size for each, while the 130PDS has a secondary of 47mm and the Tak's is 63mm. This means that the 130PDS has a total surface area of 60,033 square mm, and the Tak's has 65,562. So, with the PDS it costs about 0.38p per square mm of mirror real estate, but the Tak is 3.66p. I'm not being entirely serious here, but I am curious as to why/how what are essentially two mirrors could cost so very much more? I can understand that hi-tech or moving parts, or luxury items swathed in leather and Swarovsky command a premium. And yes, I'm sure the scope itself is made of better/more robust materials with more precise collimation and so on. But they're still just... mirrors?

No worries, I have my answers now. Everyone's been very helpful, as usual.

Fabulous. Thank you!

Great response, thanks Olly. Quick thought though: when you say that the luminance data would come through from the OSC, would that still be the case if the OSC image was blurred? Because that's what I've done in the examples above, precisely to get around that problem. I can still see that this idea might not work though. Thanks for the honest opinion!

Thanks! I can see that it's definitely better with two scopes, but I'm unlikely to be doing that. Also, getting the same FOV and orientation would be tough (it took a while to align the examples I gave) but I daresay the colour shot doesn't have to be pixel-perfect. Hmmm, food for thought...

Thanks! I use StarTools which seems to bring out the colours nicely. Having said which, I never seemed able to get enough of the nebulosity towards the outer fringes of the Rosette which I see other people getting. You're right about the Andromeda shot - well spotted! It's a mosaic of four shots for the skies around it, plus a central pane which I captured much more time on. Here it is:

OK, so it's a bad idea.