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Best Telescope for under 1400$.

by themadquark
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glappkaeft
#19
Feb7-14, 12:32 PM
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Quote Quote by Chronos View Post
The only advantage of a CCD is (...) somewhat better pixel density
And this just depends on which CCD camera you are looking at. You can easily find CCD sensors with pixel sizes from 3 to 24 microns. Pixel density is not a good metric for astrophoto since pixel size should be matched to to the focal length of the scope and the pixel scale you desire.
russ_watters
#20
Feb7-14, 02:26 PM
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Quote Quote by Drakkith View Post
I'm not sure I agree with this.
Me neither. The most basic problem here is that it is an incorrect/false dichotomy. A DSLR is a type of camera while a CCD is a type of chip. Dedicated astrophotography cameras are usually CCD but not always and DSLRs are more usually CMOS (the other type of chip), but not always. Much of the early breakout work in amateur astophotography was done using using a certain Philips webcam with a CCD chip. And many astrocams and DSLRs even use exactly the same chips. The main difference is the electronics and accessories you get with them (in particular, built-in cooling capability on an astrocam is a big deal).

Here's a cnet discussion of the issue of CMOS vs CCD for DSLRs:
http://reviews.cnet.com/4520-7603_7-6241014-3.html

Obviously, the only real con for CCDs is the price: power consumption is not an issue for a camera that is always plugged-in. But image quality is much better and the difference is much larger for long exposure astrophotography.

Bottom line: if you already have a DSLR, start with it. If you don't, I'd start with a low-end (even used) solution such as a webcam (planetary photos only) or dedicated astrocam.
davenn
#21
Feb7-14, 03:33 PM
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Me neither.

there's good advantages to having a dedicated astro imager camera
They are smaller - dont impede movement of the scope to any degree, unlike a heavy DSLR
They are lighter - dont upset the balancing of the scope to any degree, unlike a heavy DSLR
They are easier to mount to the scope optical path --- because they are specifically designed for the purpose
Altho you can, if you wish, spend a small fortune on a hi grade astro imaging camera, there are many out there that are very affordable for the amateur astrophotographer

EDIT ohhh and one more important thing....

They are easier to cool to reduce thermal noise ... using peltier cooler, liquid nitrogen ... etc

cheers
Dave
Drakkith
#22
Feb7-14, 03:46 PM
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In my opinion, the biggest advantage to having a DSLR is that you can use it for taking pictures without using a telescope. You know, family gatherings, christmas, birds, etc.
Chronos
#23
Feb8-14, 01:26 AM
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I concede. Obviously, it is smarter to blow a grand or two on a ccd before you know crap about AP. What was I thinking?
davenn
#24
Feb8-14, 01:53 AM
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Quote Quote by Chronos View Post
I concede. Obviously, it is smarter to blow a grand or two on a ccd before you know crap about AP. What was I thinking?
like I said, there are many units affordable to the amateur astronomer, you dont have to spend a fortune


Dave
Drakkith
#25
Feb8-14, 02:07 AM
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Quote Quote by Chronos View Post
I concede. Obviously, it is smarter to blow a grand or two on a ccd before you know crap about AP. What was I thinking?
I think most of these are just fine for starters. Besides, DSLR's aren't exactly a couple of bucks either.

http://www.telescope.com/Astrophotog...as/pc/4/58.uts
davenn
#26
Feb8-14, 02:50 PM
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nice one Drakkith

many of those ones were also in my link

yup for less than ~ $500 there is reasonable range to choose from. I really prefer the dedicated astro cameras
particularly for that point two I made in post #21, they are small and light and dont screw around with the telescope balancing to any great extent

Dave
Chronos
#27
Feb12-14, 11:45 PM
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The vastly wider FOV of a DSLR begs for intro AP. Cropping is no big deal when you can actually center the object of interest. You can get an excellent DSLR body for less than $500, and can be modified for even better AP performance for a couple hundred more. A similar CCD camera starts between 2-3K, and is useless for purposes other than AP. There are no balance issues on a good mount. At worst, you might need a few ounces on the tube. If you have flex issues over an extra half a pound weight on the focuser, the camera weight is not your biggest problem.
russ_watters
#28
Feb13-14, 12:09 AM
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Oy:
Quote Quote by Chronos View Post
The vastly wider FOV of a DSLR begs for intro AP.
It isn't a wider field of view, it is - possibly (some DSLRs and asto-cams use exactly the same chips) - a wider imaging surface. Which doesn't actually help you any if you already have your telescope and camera properly matched.
Cropping is no big deal when you can actually center the object of interest.
The field of view of a telescope is fixed. A chip that is much wider than the fov just shows black space, not the desired image, so having a bigger chip does not actually help you center an object. It is just money wasted on pixels you aren't using. That's called vignetting:


Ideally, the telescope and camera are matched so the light cone diameter exactly matches the chip diagonal width.
You can get an excellent DSLR body for less than $500...
You can get an excellent astro-cam (compared to DSLRs) for less than $500....
...and can be modified for even better AP performance for a couple hundred more.
...and is already fully optimized for astrophotography and includes the proper software and adapter (costs extra for a DSLR) to make it easier to use for that purpose.
A similar CCD camera starts between 2-3K...
1. You are again confused about what "CCD" means.
2. Nonsense. A $500 asto-cam will take better astro-photos than a $500 DSLR. Repeating this wrong claim will not make it true no matter how many times you make it. Most of the pictures on my website were taken by a Meade DSI II, which cost $800 when I bought it 5 years ago and is now obsolete. Superior low-end cameras start at about $400 today. The issue here is price point vs technology. DSLRs have stuck to a $500 minimum price point with increasing performance for a decade, while astro-cams started out with minimum performance for whatever price it cost - which then dropped over the past decade. Today the astro-cam prices have bottomed-out while performance continues to increase.

I suspect the issue here is that you are simply living in the past - you aren't aware of the current state of the art of astro-cams.
...and is useless for purposes other than AP.
That one is true.
There are no balance issues on a good mount.
1. Balance has nothing to do with mount quality.
2. I thought you cared about money?
At worst, you might need a few ounces on the tube. If you have flex issues over an extra half a pound weight on the focuser, the camera weight is not your biggest problem.
I run a relatively heavy imaging train, even with a dedicated astro-cam. This isn't actually a big issue, mostly cropping-up when I start and want to align the scope with an eyepiece before using a camera or otherwise wanting to switch back and forth. Nice to be lighter, but not essential.
Chronos
#29
Feb13-14, 02:23 AM
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I agree my knowledge is dated. I do, however, know what a CCD is - a charge coupled device. A Meade CCD [I have one] has an abysmal FOV. I use it as a guide camera now on an ST80 scope. I feel compelled to ask if you would feel comfortable suggesting your current rig for a rookie AP'r, or something simpler?
davenn
#30
Feb13-14, 02:24 AM
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hey Russ

didnt know you were into astronomy let along astro-photography
a whole mass of outstanding pics on your site !! well done

cheers
Dave
russ_watters
#31
Feb13-14, 09:57 AM
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Quote Quote by Chronos View Post
I do, however, know what a CCD is - a charge coupled device.
Saying "CCD camera" in this context is confusing because an astrocam is not necessarily a CCD (though most longer exposure, higher end ones are) and a DSLR isn't necessarily not.
A Meade CCD [I have one] has an abysmal FOV.
On what type of telescope? Are you using a focal reducer? I use my C11 to take pictures of small things and my ED80 to take pictures of big things, so I cover a pretty wide range of FOVs even with a fairly small chip.
I feel compelled to ask if you would feel comfortable suggesting your current rig for a rookie AP'r, or something simpler?
No, the telescope I recommended in post #14 matches the OP's $1400 budget. He didn't say what his budget is for accessories and we didn't get much into his preference on planetary vs deep sky astrophotography so I don't have a specific camera recommendation - but I know it wouldn't be a DSLR.
Chronos
#32
Feb13-14, 04:56 PM
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I have two cameras and 3 scopes to choose from. Cameras: Meade DSI Pro ii ccd, Canon T1i DSLR. Scopes: Meade LXD75, Meade LX90 ACF and Astro Tech AT6RC. Here are the FOV stats for each combo at prime focus with no focal reducer

Cam Scope pixel size Width Height

DSI LXD75 1.68" 21' 16.9'
T1i LXD75 0.95" 75.5' 50.4'
DSI LX90 0.84" 10.5' 8.5'
T1i LX90 0.48" 37.8' 25.2'
DSI AT6RC 1.25" 15.6' 12.5'
T1i AT6RC 0.71" 56' 37.4'

The DSI Pro II is not even close to the T1i. Both cameras cost about $500 new. CCD's that approach T1i FOV, which include SBIG 8300 and QHY8, start around 2K. In my mind this is a big deal. A typical half megapixel CCD like the DSI with 8.5 um pixels [about all you can afford for $500] is not going to compete well against a 15 megapixel DSLR with 4.7 um pixels.
davenn
#33
Feb13-14, 05:20 PM
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Chronos

I think you are still not quite understanding

The field of view (FOV) that your camera will see through a given telescope is determined by physical size of the CCD/CMOS sensor and the focal length of the telescope. Note that this has nothing to do with the number of pixels. A CCD/CMOS that has 512 x 512 pixels that are 20 microns square will have exactly the same FOV as a CCD/CMOS with 1024 x 1024 pixels that are 10 microns square even though the latter CCD has four times as many pixels. This is also why binning 2x2 or 3x3 affects resolution but does not affect the FOV of the CCD/CMOS. Larger CCD/CMOS's have larger fields of view at a given focal length. You can change the FOV of a CCD/CMOS only by changing the focal length of the telescope.

you comment on the poor FOV of one of your cameras ...
A Meade CCD [I have one] has an abysmal FOV.

you are blaming the camera when you shouldn't be. The problem is in the matching of the camera and the telescope.

Russ commented on focal reducers and by using a focal reducer you shorten the effective focal length of the telescope and increase the FOV (this makes the image brighter in the process). By using a Barlow or eyepiece projection you effectively lengthen the focal length of the telescope and decrease the FOV (and this will make the image dimmer in the process). To determine the FOV for a given CCD/CMOS, note the CCD/CMOS's length and width dimensions (or diagonal) in millimeters and use the formula to determining the FOV for that CCD/CMOS through any telescope as follows:

(135.3 x D ) / L = Field of View in arcminutes

where D is the length or width dimension of the CCD/CMOS in millimetres, and L is the focal length of your telescope in inches. You can use the same formula to find the diagonal field of view if you know this dimension.

I have an app somewhere on my home computer for matching scopes and astro cameras will try and find it over the weekend

cheers
Dave
davenn
#34
Feb13-14, 05:34 PM
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here's a www page that goes into FOV's focal lengths, pixel size etc
and the importance of taking into account the type of scope a given camera goes onto

down towards the bottom of the page ... just above a table is a link to a spreadsheet showing a particular camera and how it matches to a variety of different telescopes with different apertures, focal lengths etc

After reading through that and other sites will lead you to realise that smaller pixel size is NOT always an advantage. That in some situations a smaller sensor size and larger pixels will outperform a larger sensor size and smaller pixels

cheers
Dave

EDIT ... another link of interest .... http://www.skyandtelescope.com/howto...y/3304356.html
russ_watters
#35
Feb13-14, 06:48 PM
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Quote Quote by Chronos View Post
I have two cameras and 3 scopes to choose from. Cameras: Meade DSI Pro ii ccd, Canon T1i DSLR. Scopes: Meade LXD75, Meade LX90 ACF and Astro Tech AT6RC. Here are the FOV stats for each combo at prime focus with no focal reducer

Cam Scope pixel size Width Height

DSI LXD75 1.68" 21' 16.9'
T1i LXD75 0.95" 75.5' 50.4'
DSI LX90 0.84" 10.5' 8.5'
T1i LX90 0.48" 37.8' 25.2'
DSI AT6RC 1.25" 15.6' 12.5'
T1i AT6RC 0.71" 56' 37.4'
Other than not having a focal reducer (and me not knowing the scope sizes), I'm not seeing a problem there. With a focal reducer, your 21x17 becomes about 42x34, which is near perfect for most DSOs: an awful lot of globular clusters and galaxies are in the 10-30' range.
The DSI Pro II is not even close to the T1i. Both cameras cost about $500 new. CCD's that approach T1i FOV, which include SBIG 8300 and QHY8, start around 2K. In my mind this is a big deal. A typical half megapixel CCD like the DSI with 8.5 um pixels [about all you can afford for $500] is not going to compete well against a 15 megapixel DSLR with 4.7 um pixels.
Since you have both, I'm really not understanding how you can be saying these things: have you taken pictures of the same object with both to compare them? FOV is not the only thing that should be compared between the cameras and is definitely not the most important: since the DSI is a CCD and has a heatsink, it should provide substantially better image quality. And It should also be easier to use due to the dedicated software.

When I bought my DSI cameras, FOV was not high on the list of wants.
Chronos
#36
Feb13-14, 11:28 PM
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The LXD75 is 10" f5 SN. The LX75 is an 8" f10 SCT. The AT6RC is 6" F9. A .5 focal reducer is a bad idea on an f5 scope, but, probably good for an f10 or f9. For a discussion of DSI vs DSLR, see http://cs.astronomy.com/asy/astro_im...73/420955.aspx. It's pretty much a never ending jousting match. From my POV user friendly is the number one issue for intro AP, and a DSLR wins that battle hands down, IMO. I would never recommend a CCD to a novice AP'r. That, admittedly, is a personal choice.


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