Jump to content

SkySurveyBanner.jpg.21855908fce40597655603b6c9af720d.jpg

Rho Ophiuchi peeps above the parapet.


ollypenrice

Recommended Posts

Project with Paul Kummer, who persuaded me that this was worth a try. I was doubtful, thinking it too low from Lat 44.19, but I'm glad he persuaded me. This had 2.8 hours in 3 min subs from a RASA 8 on an Avalon Linear and with ASI 2600 MC (OSC) camera. Paul managed the capture and pre-processing from the UK but the scope is located here in our robotic Observatoire Per Frejvall. This is my post processing.

We could find no way of using DBE or ABE since half of the image has no background sky, but I compared it with good images from lower latitudes and concluded that our colours and brightnesses were in decent agreement without severe gradients. This version was de-starred in StarXterminator after a partial stretch and the stars replaced at a softer stretch. I think our latitude basically cost us contrast because there is nothing in the field requiring high resolution.

1082210761_Rho_OphuichiiFINWEB.thumb.jpg.2c2cbe2bb07a76304ddf13ae90119783.jpg

Olly

  • Like 41
Link to comment
Share on other sites

1 minute ago, Tom OD said:

Great shot given the latitude. It might be a bit green  on my screen in the centre, but you nailed the contrast I think in the dark nebula areas.

Tom

Yes, I felt there was a whiff of green across the middle, going horizontally. However, trying to fix it threw the other regions out of colour balance so I decided to let it be. I didn't run SCNR green on the linear data. Perhaps I should have done.

Olly

Link to comment
Share on other sites

7 minutes ago, ollypenrice said:

Yes, I felt there was a whiff of green across the middle, going horizontally. However, trying to fix it threw the other regions out of colour balance so I decided to let it be. I didn't run SCNR green on the linear data. Perhaps I should have done.

Olly

Try SCNR on the full image, it might only adjust the middle section.

T.

Link to comment
Share on other sites

2 hours ago, Rodd said:

Your the master Olly--amazing.  A OSC at low lattitude.  5 years ago you would have called yourself crazy for thinking of it!

I thought it crazy this year, quite honestly, Rodd. :D And I thought the processing would all be about gradient removal. In fact, this hasn't had any because I couldn't find any way to do it. This wasn't a complicated image to process, really.

Olly

Link to comment
Share on other sites

1 hour ago, ollypenrice said:

I thought it crazy this year, quite honestly, Rodd. :D And I thought the processing would all be about gradient removal. In fact, this hasn't had any because I couldn't find any way to do it. This wasn't a complicated image to process, really.

Olly

The million dollar question….OSC or mono?

Link to comment
Share on other sites

3 hours ago, ollypenrice said:

OSC.  Filters and the RASA carry too much baggage.

Olly

With the rasa. Or hyperstar.  How about in general?  That is where all this is headed.  Are we there yet?

Link to comment
Share on other sites

1 hour ago, Rodd said:

With the rasa. Or hyperstar.  How about in general?  That is where all this is headed.  Are we there yet?

With dual or tri-band filters available I think we're getting very close. Maybe fast optics are also important (I don't know) and the aim needs to be enhanced broadband rather than pure colour mapping.

Olly

Link to comment
Share on other sites

  • 3 weeks later...
On 07/07/2022 at 15:14, tomato said:

Wonderful. In addition to your dark sky you are also blessed with unobstructed horizons, if I recall correctly.  The lowest elevation I can use is 18 degrees. 🙄

Our horizons are variable. There's a huge lime blossom tree to the north but this doesn't really matter because the circumpolar objects always rise above it and are at their best when they do. In the south we can go to horizontal in one place and to about 10 degrees around that. The western horizon rises to 20 degrees but that just shortens the imaging time available on an object. It doesn't exclude anything. With proper planning you can leave red till last and catch that at lowest elevation where you don't really lose much of importance. Depending on the target, this also applies to Ha, certainly in the case of galaxies where the Ha tends to be fairly blob-like at best! 😁

Olly

Link to comment
Share on other sites

damn you Olly - you got me thinking about 2600s again... I do like using my 533 OSC, but I hate the limited resolution compared to my 1600 (i.e. once you include bayer matrix is much lower).

So.. of course I popped over to FLO just to see how much they cost these days - and they have a customer return with 500 quid off, full warranty.

Well.. they don't anymore.

😁

Edited by powerlord
  • Like 2
Link to comment
Share on other sites

3 hours ago, powerlord said:

damn you Olly - you got me thinking about 2600s again... I do like using my 533 OSC, but I hate the limited resolution compared to my 1600 (i.e. once you include bayer matrix is much lower).

So.. of course I popped over to FLO just to see how much they cost these days - and they have a customer return with 500 quid off, full warranty.

Well.. they don't anymore.

😁

I'm not persuaded by the theory that the Bayer Matrix significantly reduces resolution. When I had both mono and OSC Atik 4000s I looked for such a reduction and couldn't find it. Of course, in strict terms, the matrix does reduce resolution, more in red and blue than in green, since there are two green pixels per red and blue. However, the debayering algorithms interpolate what is likely to be missing in between filters of a given colour and restore it. The edge of an Ha structure in a nebula will be picked up on one pixel in four but interpolation will fill in that edge. Not all debayering programs are equal but I think that, in reality, they are so good as to bring the result to a standard imperceptibly inferior to monochrome luminance. If the system is over-sampled, as is becoming increasingly likely with tiny CMOS pixels, there will surely be no possibility of distinguishing between the resolution of OSC and mono. I've long advocated mono over OSC in CCD days but this was on the grounds of light reaching the chip. I always conceded that they were effectively equivalent in resolution.

All the images I've posted from the RASA have been resampled downwards. It is not oversampling on paper but, when you look closely at the data, it very clearly is oversampling in reality and there is nothing to be gained by finishing an image at full size.

Also it might be worth thinking about the stunningly high resolution we obtain easily from DSLRs. They are nearly all OSC chipped cameras...

Olly

Link to comment
Share on other sites

I did some side by sides - 1600 vs 533 of M16 and there was lots more detail in the 1600 Ha. Now, of course slightly different fov, etc, etc - but does seem to me that 9mp/4 = 2.25mp  is gonna be less sharp that 12mp surely ? At least that's what I found.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
  • Recently Browsing   0 members

    • No registered users viewing this page.
×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. By using this site, you agree to our Terms of Use.