Quote:
Originally Posted by glend
Yes i am doing it. I use a Bresser 152mm f5 (Flatfield achromat with modified Petzval design). Importantly it has a very strong Hexfocuser that can support an imaging train. Purchased from Teleskop-Express at a rediculously low price, unavailable from suppliers outside europe. BTW Teleskop-Express remove the 19% Euro VAT when they sell out side the EU, this offset pays for the shipping.
https://www.teleskop-express.de/shop...0-mm--OTA.html
No CA issues obviously as i am narrowband only with this scope. Surprisingly there turned out to be little focus difference, especially with Ha and Sii filters which are very close in the spectrum. Yes Oiii requires a focus check. I use a bahtinov mask to check focus when i switch filters. Importantly my Baader NB filters are parafocal and that helps. I tend to shoot Ha and Sii back to back on the same night and do Oiii another night, this cuts the need to refocus. You don't need a motor focuser if your prepared to do it manually, and the Bresser focuser easily supports my ASI1600MM-C and the QHY filter wheel - no sag, no tilt.
IMHO you would need to invest in proper narrowband filters. You can build a synthetic luminance layer with NB filters, particularly Ha and Oiii, but i find using Ha as luminance works pretty well.
I would not recommend trying LRGB imaging through any achro, but others might. |
thanks glen looks like an interesting scope quite fast for a refractor as well. from what I read the focuser and options for upgrading can be limiting so good to hear your experience with that model.
I think L-RGB imaging is definitely out, really interested to hear about any RGB experiences.
Quote:
Originally Posted by RickS
I've done a few RGB only images with data from our automated/shared scope at SRO. In terms of detail there's a benefit as we get better FHWM in the colour subs that we do in Lum. For bright objects it works well. I did a very decent M31 with about 6 hours on each colour. The downside is that it does take substantially longer to get good SNR with dim targets.
Cheers,
Rick.
|
Quote:
Originally Posted by RickS
Just happened to have some data that I'm working on right now. The target is NGC7497, a small galaxy visible through lots of dust. I extracted luminance from just over 31 hours of RGB data and compared it to just over 9 hours of real Lum. The SNR estimated by PI/SubframeSelector is about the same and eyeballing them they look very similar.
Of course, the luminance I'm actually working with is a combination of both 
Cheers,
Rick. |
awesome timing - thanks for the info Rick - it sounds a bit like OSC capturing as far as total integration times go