Stargazing Which Telescope Under $1400 Offers the Best Planetary and Deep Space Viewing?

[russ_watters]

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]

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]

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]

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 realize 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/astrophotography/3304356.html

 

[russ_watters]

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]

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_imaging/f/15/p/41073/420955.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.