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Old 13-07-2017, 07:03 PM
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astronobob (Bob)
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Imaging with 12"SCT & 3.3 Reducer, How Feasible ?

Hi All,
I am considering Imaging with this 12" SCT & 3.3 x Reducer, for a few reasons, well, F/ 3.3 cant be 'snubbed-off' easily, in my books anyway,
Also, guiding tolerances would not be nearly as critical compared to F10 - 3 meters compared to around 1 meter ?
Also a much smaller - 'Mini-Guider' would save a heck of a lot of weight, enabling my Neq6 to cope with ?

Just thought to ask, & it really doesn't matter what mount is being used, but mainly the Performance of the typical Meade 3.3 Reducer in a photographical sence, , does it need a flattener, even tho my 12" SCT is an ACF version, which produces flat field & point stars to the edge, but I havent used any 6.3 reducer, so not sure of the effects either reducer has on the image plane ?

Do they magnifies any 'non existant' curvature at F10 which may show up at F6.3 or even worse/more at F3.3 ?

12"@ F3.3 would definitely 'hurry-along' the photon collection
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  #2  
Old 13-07-2017, 08:09 PM
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multiweb (Marc)
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Quote:
Originally Posted by astronobob View Post
Hi All,
I am considering Imaging with this 12" SCT & 3.3 x Reducer, for a few reasons, well, F/ 3.3 cant be 'snubbed-off' easily, in my books anyway,
Also, guiding tolerances would not be nearly as critical compared to F10 - 3 meters compared to around 1 meter ?
Also a much smaller - 'Mini-Guider' would save a heck of a lot of weight, enabling my Neq6 to cope with ?

Just thought to ask, & it really doesn't matter what mount is being used, but mainly the Performance of the typical Meade 3.3 Reducer in a photographical sence, , does it need a flattener, even tho my 12" SCT is an ACF version, which produces flat field & point stars to the edge, but I havent used any 6.3 reducer, so not sure of the effects either reducer has on the image plane ?

Do they magnifies any 'non existant' curvature at F10 which may show up at F6.3 or even worse/more at F3.3 ?

12"@ F3.3 would definitely 'hurry-along' the photon collection
I'd say it would be close to a miracle to get a flat field on an SCT reduced to F3 at prime. Why not use an hyperstar which has better correction if you want to go that fast?
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Old 13-07-2017, 08:20 PM
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Atmos (Colin)
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Not sure what the correction is like on that F/3.3 reducer BUT I know the imaging circle is tiny, thinking about the same size as a guide camera chip!
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Old 13-07-2017, 08:37 PM
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redbeard (Damien)
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Hi Bob,

First of all I only know a little about this but here goes:

The 3.3 has been around for a while and when it first came out, and for a while later, the CCD sensors on cameras were very small. Worked well back then, but I think that you would get a lot of vignetting with today's size sensors.

I have the GPS LX200 10" and almost always use the 6.3 reducer which is also meant to flatten a little as well and that works well. In the Meade 3.3/6.3 manual, it states that they both do some flattening so you may not want that with your ACF.

It's always nicer for a faster image though, and I can recommend the AstroPhysics - CCD Telecompressor(CCDT67). Same as focal reducer.
No flattening.

From their website
http://www.astro-physics.com/product...&%2027TVPH.pdf

But hey, if you have a 3.3 or can borrow one, then give it a go. Then you will know exactly how it works with your gear. I did that...once.

Cheers,

Damien.
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Old 15-07-2017, 12:03 PM
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astronobob (Bob)
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Quote:
Originally Posted by multiweb View Post
I'd say it would be close to a miracle to get a flat field on an SCT reduced to F3 at prime. Why not use an hyperstar which has better correction if you want to go that fast?
Cheers Marc, interesting none the less, guess its something one needs to experiment with, if plausible, & tho am preferring near the 1mt F/L at moment as well, it may be another option
------------------------------------------------------
,
,


Quote:
Originally Posted by Atmos View Post
Not sure what the correction is like on that F/3.3 reducer BUT I know the imaging circle is tiny, thinking about the same size as a guide camera chip!
Thanx Colin, wow, I didnt enter the idea of considering the Image circle, , never have actually !
Sounds like it has a rather intense effect in this situation
--------------------------------------------------------
,
,

Quote:
Originally Posted by redbeard View Post
Hi Bob,

First of all I only know a little about this but here goes:

The 3.3 has been around for a while and when it first came out, and for a while later, the CCD sensors on cameras were very small. Worked well back then, but I think that you would get a lot of vignetting with today's size sensors.

I have the GPS LX200 10" and almost always use the 6.3 reducer which is also meant to flatten a little as well and that works well. In the Meade 3.3/6.3 manual, it states that they both do some flattening so you may not want that with your ACF.

It's always nicer for a faster image though, and I can recommend the AstroPhysics - CCD Telecompressor(CCDT67). Same as focal reducer.
No flattening.

From their website
http://www.astro-physics.com/product...&%2027TVPH.pdf

But hey, if you have a 3.3 or can borrow one, then give it a go. Then you will know exactly how it works with your gear. I did that...once.

Cheers,

Damien.
Hi Damien, & I much appreciate your feedback here, all very worthy of mentioning
I should atleast try giving my 6.3 a go with imaging, and see what it produces.. Then take it from there
Good Stuff
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Old 15-07-2017, 12:37 PM
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Ive got 3X different 3.3reducers. Live imagers love them on 1/3" sensors. Makes any scope (eg SCTs) really fast for stacking those 2-10sec subs. There's not too much coma with this size sensor ...

Last edited by ChrisV; 15-07-2017 at 01:15 PM.
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Old 15-07-2017, 03:41 PM
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Hi Chris , , Thanx for your valued input


Soo, your saying you have a 3x reducer, different to the 3.3, is this correct,, and if so, do you have a link to it or sale company that has them, even the 'brand' of it would suffice ?

Sounds interesting and I am happy to crop the final image if the data collection is not coma effected to far in from the edge of the QHY10 sensor
(APS-C size) Sony with a 1.5 crop factor, which of-top-of-head is 22mm long side.

Cheers and thanx for any further insight you may able to offer
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Old 15-07-2017, 04:30 PM
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Sorry. I meant that I have three different F3. 3 reducers.
Two different meades and an optec.

As others mentioned they can really only be used on small sensors - I'm sure it was specifically 1/3". Anything bigger than that = coma city (apparently).

But if you got one. Give it a go and show us! Be interesting to see how much of an aps-c shot is coma free.

I alter the camera-sensor distance to get different amounts of reduction - so my meade f3.3 I use anywhere from 0.7 to 0.33 reduction. I should have some old shots with the meade on a C8 somewhere - using a 1/3" camera.

Last edited by ChrisV; 15-07-2017 at 04:54 PM.
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Old 15-07-2017, 08:48 PM
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Quote:
Originally Posted by ChrisV View Post
Sorry. I meant that I have three different F3. 3 reducers.
Two different meades and an optec.

As others mentioned they can really only be used on small sensors - I'm sure it was specifically 1/3". Anything bigger than that = coma city (apparently).

But if you got one. Give it a go and show us! Be interesting to see how much of an aps-c shot is coma free.

I alter the camera-sensor distance to get different amounts of reduction - so my meade f3.3 I use anywhere from 0.7 to 0.33 reduction. I should have some old shots with the meade on a C8 somewhere - using a 1/3" camera.
Ahh, cheers Chris, my bad, Lol
Yes, might be very interesting - and I appreciate your further input on amount of reduction,,, May I ask how much distance the reducer is positioned away from the sensor to achieve a 0.7 reduction and distance for 0.33 reduction, no need be spot on but ball-park-figures would be as useful for this duck If cant, that is all good all the same

I currently have the 10" Newt on my pier, but its being problematic at the moment, Soo, the 12" could be going back on again sooner than later
Cheers
Bob
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Old 16-07-2017, 09:48 AM
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ChrisV (Chris)
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Bob

Do you already have the reducer? If so, try it. The meade comes with the T-SCT adaptor and a few spacers.
But if you have the 6.3 I'd definitely try that first. It uses much longer spacing than the 3.3, and will produce much less vignetting.

I don't have an SCT anymore so dont remember what spacing I used. And it also depends on what backfocus your camera has. If you are using a dslr it could be aproblem as they have a really long backfocus (I suppose).

I connect scope to reducer to t-SCT adaptor to spacer to camera. I took a shot with out the reducer, then with the reducer with no spacer, then kept increasing the spacer until the image was crap. Bang the images into astrometry.net and you can work out the reduction.

Just try what you got first. If no good, then try what the others have mentioned - they know a lot more than me.

Chris
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Old 17-07-2017, 06:53 PM
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astronobob (Bob)
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Cheers again Chris and yep, I will eventually give this a go, but for now, Im sorting the 10"Newt.
The main reason for my 'Topic of this thread' questions is that I was about to sell this 12" Meade sct acf, but I am having real 2nd thoughts, and am going to pull-out of the sale, It is just such a beautiful scope, for this duck anyway, lovely with visual views as one can imagine !
Thanx so much for helping me realise, I must try a few things with it - so be it - down the track !!


Quote:
Originally Posted by ChrisV View Post
Bob

Do you already have the reducer? If so, try it. The meade comes with the T-SCT adaptor and a few spacers.
But if you have the 6.3 I'd definitely try that first. It uses much longer spacing than the 3.3, and will produce much less vignetting.

I don't have an SCT anymore so dont remember what spacing I used. And it also depends on what backfocus your camera has. If you are using a dslr it could be aproblem as they have a really long backfocus (I suppose).

I connect scope to reducer to t-SCT adaptor to spacer to camera. I took a shot with out the reducer, then with the reducer with no spacer, then kept increasing the spacer until the image was crap. Bang the images into astrometry.net and you can work out the reduction.

Just try what you got first. If no good, then try what the others have mentioned - they know a lot more than me.

Chris
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