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Bagnaj97

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About Bagnaj97

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    Nebula

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    Ashford, Kent
  1. Skywatcher ST80 & Ultrastar

    The filters may be parfocal, but the telescope isn't so you still need to refocus. The reason apochromatic refractors are much more expensive is that they have more lens elements and usually more exotic types of glass in order to bring more wavelengths of light to focus at the same point. https://computerphysicslab.wordpress.com/2010/10/14/apochromatic-vs-achromatic-refractor/ has some good example images.
  2. Skywatcher ST80 & Ultrastar

    The ST80 is achromatic, which means that the different wavelengths of light aren't all brought to focus at quite the same point, so you get colour fringing (usually seen as blue halos around stars). That's why your L subs make things worse - the stars will be very bloated because of some wavelengths being out of focus. RGB can be done, but you have to refocus for each colour filter. For primarily red objects, i.e. emission nebulae, you can use the red filter (or, even better, Ha) for luminance, which helps the nebula pop out of the background. Take lots more R subs, but when stacking use an equal number of subs for RGB and all of the red ones for L. This won't work for broadband objects like galaxies though.
  3. Hmm, now I've had an idea... 3xST80 (R, G, B or SHO), 3d-printed tube rings and cheap guidecams (touptek, ASI120mm, QHY5l II etc). Tempting...
  4. I was poking about on Aliexpress and stumbled across a couple of interesting items. An awfully convenient way to get quick LRGB images! https://www.aliexpress.com/store/product/ASTROSHOP-telescope-ARRAY-TA-70/1371081_32823628159.html 4 70mm quadruplets https://www.aliexpress.com/item/Astroshop-telescope-ARRAY-TA-80/32816662435.html Or 4 CF 80mm triplet APO 'fracs, optionally supplied with a QHY163m each. Anyone want to buy me one? Although my AVX may struggle a little...
  5. QHY163m with 1.25" filters

    I got hold of the M42 Big Screw adapter from Modern Astronomy and it's helped, but there's still a little vignetting that's hard to get rid of, but I can live with it. WIP Jellyfish (needs a lot more data!) - http://astrob.in/319442/0/ M33 Triangulum - http://astrob.in/318998/B/ M31 Andromeda - http://www.astrobin.com/full/309974/B/ Vignetting is visible in the corners on the right hand side of Jellyfish and M33 but not the left and it's consistent, which suggests my filter wheel isn't quite lining the filters up centrally. If the filters were more central and the vignetting equal across all the corners it would likely be a non-issue. I can't see the vignetting in the Andromeda pic, but I've had all sorts of trouble getting the colour ok-ish on it, so I've done all sorts of background removals etc. So in my opinion the QHY163m can be used with 1.25" filters, as long as you're at f/6 or slower. If you're buying everything from scratch then save your pennies for a bit longer and get 2" filters.
  6. M33 Triangulum Galaxy HaLRGB

    Reduced red a bit further and upped the blue slightly, I think it looks more natural now.
  7. M33 Triangulum Galaxy HaLRGB

    Attempt number 2, I'm much happier with it now, but there still seems to be a bit of green around the galaxy that I'm struggling with and I'm not sure if I've got a bit too much red now... I've already knocked the red down but with a star mask in place to protect them, as the star colours seem ok. The full uncropped version is on astrobin www.astrobin.com/318998/B/
  8. M33 Triangulum Galaxy HaLRGB

    It was a quick process after capturing to see what I'd got before going to bed, as I don't have time this weekend to tackle it properly. Batchpreprocessing, lrgbcombination, nbrgb script to add the Ha, photometric colour calibration, arcsinhstretch, increased saturation. Also some sort of denoise in there but I don't remember which or when. As I understand it PCC means the star colours should now be correct, so if I remove the green the stars will be off. Time to figure out a starmask in PI I guess, unless I've missed something? Iirc there's a 'background correction' option or similar in PCC which I left ticked. Perhaps I'll try turning it off, and then doing a dynamic background extraction in instead.
  9. I think I'm starting to get the hang of this mono imaging business. Guiding was bad, I'm not sure if it was a balance issue imaging quite near zenith, or if it was cable drag, but I was getting a big sawtooth pattern in dec later on. Full details and full size image on astrobin http://www.astrobin.com/318998/ Just a slight improvement over my last attempt in Nov 2016. C6n, modified 450d, AVX, unsure on exposures now.
  10. If you've got a battery box it might be easier to build the controller in rather than messing with cigarette plugs. The dew controllers are on the right in these pics of my battery box:
  11. I don't have one for sale, but they're relatively easy to make. 1x suitable container (tupperware etc) 1x http://www.ebay.co.uk/itm/3Meter-Car-Cigarette-Lighter-Power-Male-Socket-Plug-Connector-LED-Switch-12V-24V-/152609874827 2x http://www.ebay.co.uk/itm/20A-DC10-60V-PWM-HHO-RC-Universal-Motor-Speed-Regulator-Controller-Switch-/132302230892 1x http://www.ebay.co.uk/itm/Pair-RCA-Female-to-Screw-Connector-Terminal-Phono-Socket-Audio-CCTV-Camera-UTP-/362023824425 for ease, or http://www.ebay.co.uk/itm/05082PI-10x-RCA-Phono-Chassis-Panel-Mount-Female-Socket-Metal-Red-Connectors-/272013876911 if you want to mount the connectors on the box/container, but soldering is needed. and if you're not in a hurry you can order the parts from china (either ebay or aliexpress etc) and it'll cost even less.
  12. Brought my first scope!

    and get yourself a red headlamp so you can see without damaging your dark adaptation too much. This is the one I've got and contains an internal USB rechargeable li-ion battery - right button controls the red LEDs, left controls the white LEDs, unlike some where you have to cycle through white to get to red. This appears to be the same but runs on AAA batteries if you prefer. You'll need a T-ring to attach your DSLR to the telescope, if you've got Amazon prime This is the cheapest non-ebay one I could find. Unscrew the 1.25" holder from the focuser and the T-ring should screw into place. Later I'm sure you'll want to add a coma corrector, but that'll get you started.
  13. About EQ3-2 weight limit

    What about a 5" SCT? The Celestron C5 has a longish FL (1250mm) for planetary, although not quite as long as the Mak (1500mm), but if you add the Celestron 0.63x reducer/corrector you've then got a focal length of 787.5mm at f/6.2 - well into 150p territory, whilst being lighter than the Mak127 or 150p(ds).
  14. 3D printing for accessories? Or other materials?

    My piggyback tube rings are still fine, with ED80, ST80, QHY163m, filter wheel and dew tapes hanging off now. - https://www.thingiverse.com/thing:2181161 It helps that I massively over-engineered them - the plastic is very thick and the overall weight is probably comparable to a similar conventional system. The primary benefit was cost, a roll of filament is cheap compared to all the rings and dovetails needed, but it was also satisfying making my own.
  15. I bought the finder you're talking about recently and it's terrible. If you've got a standard Synta 6x30 finder then you can unscrew the objective cell and replace the one on the Seben. The threads aren't quite right, but it seems to work. Image quality is far better than the stock Seben and you get the benefit of RACI, but personally I'd save your pennies for a "proper" RACI finder.
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