Jeffkop
member
Reged: 05/06/08
Posts: 15
Loc: Alstonville NSW Australia
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Hi again to the community
I have an ST2000XM with a set of CS RGB and Clear filter set that I purchased from SBIG. The clear filter has no IR block. I was hoping to get some input into a comparison of this set to an Astrodon i series LRGB set. The CS ones are supposed to be parafocal .. but Im sure I have to refocus when I select the red filter.
Any feed back would be great
Thank You
Jeff
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gordianknot
sage
Reged: 09/04/05
Posts: 398
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What kind of telescope are you using? If it doesn't have good color correction, it may be that the colors get focused to different slightly different planes even if the filters are parfocal.
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Jeffkop
member
Reged: 05/06/08
Posts: 15
Loc: Alstonville NSW Australia
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Sorry .. see newcomers to this pastime always get caught out. When I was having the trouble Im talking about I was using a MAK180PRO .. Skywatcher Mukasatov 180mm. NOW I have bought a Tak TSA102 .. still waiting for G11 mount to arrive to give it first light. Hopefully this helps
thanks
Jeff
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roestman
super member
Reged: 12/18/06
Posts: 113
Loc: Houston Texas
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hello
i use the Astrodon i series LRGB set with my st02000xm.
i nearly always re-focus on every filter change, but there have been times when i have not. the parafocal seems ok for my set up.
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Rick
TAK TOA-150
12.5" RCOS truss, waiting for construction
C9.25 f/10
WO Zenithstar 110
WO Zenithstar 80
Orion ST 80
Meade Lx3 10"
SBIG ST-2000XM CFW-9 w/ Astrodons
OPTEC TCF-S
AO-8
Meade DSI Pro
DSI Pro 2
DSI COLOR
Canon XTI
Takahashi EM-200
Paramount ME
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emutz
sage
Reged: 02/15/06
Posts: 267
Loc: Pensacola, Fl
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I had CS filters where the color filters were parfocal. However, I discovered too late that the Ha, OIII, SII CS filters were not parfocal withthe color filters. I found this pretty annoying. Eventually, I sold the CS filters and bought a set of Astrodon E-series filters. Now everything is parfocal. The color sub images with my ST-10 seem a little brighter (especially with the blue channel) than with the CS filters. Astrodons promise a 1:1:1 RGB exposure ratio. However, I have not found this to be true. While I expose the same number of B,G,R subs, I always have to adjust the blue ratio to around 1.4 in Maxim when doing a color combine.
Overall, I like the Astrodon's better, mostly because they are parfocal, not because the images seem to have better color.
Just my 2 cents....
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Rick J
sage
Reged: 03/01/08
Posts: 204
Loc: Mantrap Lake, MN
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I don't like a clear filter without IR block for LRGB images as the Lum image then picks up IR features not seen in any of the RGB filters.
With my STL-11000XM and 14" LX200R I see no focus issues with the 5 Astrodon filters in my filter wheel. LRGB and Halpha. BUT I do see a bit of chromatic problems in blue light that actually causes it to be slightly smaller image scale by about 3 pixels horizontally and 2 vertically that I have to compensate for. Very weird and unexpected. I borrowed a CS blue filter and it too came out the same scale as my Astrodon so it's in the scope not the filter. I assume this fuzzes up the Luminosity image slightly but when I make a pseudo luminosity image out of red and green filtered images it seems No sharper. It's a puzzle I've not solved.
I have imaging friends who you couldn't pay to use Astrodon and others who feel the same about CS. Others prefer some other brand. I think it is what you are used to and have learned to use that's most important. I borrowed 4 different brand sets when getting into digital from film. I saw so little difference I bought the one I found the best buy on on AstroMart. It happened to be Astrodon I series. The seller decided he liked another brand better. The price was good so that's what I bought and learned to use.
Rick
Edited by Rick J (05/17/08 09:56 PM)
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Dan G
scholastic sledgehammer
Reged: 06/27/06
Posts: 978
Loc: Minisink, NY, USA
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Jeff -
Welcome to CN!
I had the Schuler and found the lack of parfocal irritating. Switched over to the Astrodon i series and have been very pleased. The RGB is much better balanced with the Astrodons. I needed to take 2x the exposure time with R with the Schulers. The Astrodons are close to 1:1:1
Dan in NY
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TV 76, Vixen VC200L, TV NP-127is
EM-200, NJP
ST-2000xm and ST-402
Tranquility Base Observatory aka "The Shed" by non-tranquil members of the house
www.nyskies.com Still a work in progress!
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Jeffkop
member
Reged: 05/06/08
Posts: 15
Loc: Alstonville NSW Australia
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Thanks everyone so far for your inputs. You learn ALL the time in this game, and I guess I should have explored the world of filters a little more instead of just going with what the SBIG salesman said, my biggest concern here being the apparent different focus's and the non IR blocked clear filter. I read different opinions on whether one has IR or non IR luminance images. I DO get some reasonably severe blooming in some targets and it detracts from the whole picture in the end. Also I find now I think of it that when I colour combine in Maxim .. the blue dots always seems bigger and so, some, not all stars have a blue tinge on mostly one edge. Frustration is a word Im seeing a LOT of in posts ... I know why now ... the universe does not give up her secrets easily, tis for sure, however THAT just makes me MORE determined to conquer it.
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Dean
Post Laureate
Reged: 12/31/04
Posts: 4232
Loc: Bailey Co Elev 8780 feet
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Quote:
I read different opinions on whether one has IR or non IR luminance images.
Generally you want IR blocking if you use a refractor. Don Goldman has a good article on using IR here.
I went through 2 sets of CS filter with my ST10, but both sets had light leaks and I switched to Astrodons and use Astrodons with my STL11K as well. The ST10 is much weaker in blue and with the CS filters I had to shoot twice as much blue as R&G. With the Astrodons I shoot the same amount of blue as R&G.
The CS and Astrodons I've used were close to parafocal, but not quite. What I do is focus with clear and then use an offset for the different filters so I don't refocus, just move the focuser a tad.
Don Goldman posted some interesting info on parafocal filters on the Yahoo SBIG group here
One thing to keep in mind, a shorter FR means a narrower zone of focus which will make the filters less parafocal than longer FRs.
I still use a CS Ha filter with my ST10. It's focus is quite a bit different that my LRGB filters (both the CS and Astrodons). I use an Astrodon Ha filter with my STL11K and it is very close to the Astrodon LRGB filters which is nice.
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deanrowe.net/astro
FWHM Imaging Forums
Whats with that avatar?
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roestman
super member
Reged: 12/18/06
Posts: 113
Loc: Houston Texas
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Quote:
Quote:
What I do is focus with clear and then use an offset for the different filters so I don't refocus, just move the focuser a tad.
Jeff
This hobby has a large learning curve. I have yet to post any images as I am still at the bottom of the curve. Dont let your self get frustrated. It all works out with time and trial and error.
not to jack Jeff's post but
Dean
How are you calculating your offset for focus.
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Rick
TAK TOA-150
12.5" RCOS truss, waiting for construction
C9.25 f/10
WO Zenithstar 110
WO Zenithstar 80
Orion ST 80
Meade Lx3 10"
SBIG ST-2000XM CFW-9 w/ Astrodons
OPTEC TCF-S
AO-8
Meade DSI Pro
DSI Pro 2
DSI COLOR
Canon XTI
Takahashi EM-200
Paramount ME
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Dean
Post Laureate
Reged: 12/31/04
Posts: 4232
Loc: Bailey Co Elev 8780 feet
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Quote:
Dean
How are you calculating your offset for focus.
I don't calculate it, I measure it. I use a PDF & FocusMax, so it's simply a matter of have FM focus with one filter as the baseline (offset = 0 - I use clear for this), note the position, and then focus with another - the offset is the difference in the focuser position. I do it several times to get a good sample.
One thing that's handy about doing this, is with my ST10 there's a big difference between the Ha and LRGB filters (250 microns), but knowing the offset means I can focus with the clear filter and add the offset rather than try and focus with the Ha filter which takes a fairly bright star. It also means I can shoot HaRGB sequences without having to refocus between the Ha and RGB (although when I shoot Ha, I usually shoot just Ha).
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deanrowe.net/astro
FWHM Imaging Forums
Whats with that avatar?
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roestman
super member
Reged: 12/18/06
Posts: 113
Loc: Houston Texas
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thanks
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Rick
TAK TOA-150
12.5" RCOS truss, waiting for construction
C9.25 f/10
WO Zenithstar 110
WO Zenithstar 80
Orion ST 80
Meade Lx3 10"
SBIG ST-2000XM CFW-9 w/ Astrodons
OPTEC TCF-S
AO-8
Meade DSI Pro
DSI Pro 2
DSI COLOR
Canon XTI
Takahashi EM-200
Paramount ME
|
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