Posts Made By: Hal Coward

I am interested in an autoguider which will also serve for lunar and planetary imaging and stellar photometry. For wide-angle deep sky I'm still into film. I am considering three alternatives:

1) STV

2) ST5C

3) ST237A

The STV is stand-alone, but more expensive. Including the price of a laptop (which I would have to buy), alternatives 2 and 3 cost about the same to a little more but carry greater power requirements. As I understand the literature, I could run the STV off a 12-volt power source (like the one I use for my mount).

I'm leaning toward the STV, but wonder what the experienced hands can tell me might be the other tradeoffs between the alternatives. No color with the STV is one, but I'm sure there are others. I wonder in particular about ease of focusing. Thanks for any helpful comments.

Hal Coward

Tak FS128, LE 18mm eyepiece, Tak digital camera adapter
Sony 707 camera at ISO 100 and 1/10 sec exposure

Has anyone tried the new (to me, at least) Kodak High Definition 400 film? Any worthwhile results?

Hal Coward

Hi Ivan,

I'm no optical expert, but I think it is essentially as you describe. Attached is a 35mm lunar shot through a Mewlon 180, vari-extender, and three extender rings for an effective focal ratio of f36. Gives an idea of image scale. The original film image is much sharper - my inexpert scanning and reduction of file size has blurred it considerably.

Hal Coward

Hi Chris,

What I find very appealing about these images is that they approximate what can be seen visually with sufficient aperture. Cool.

Hal Coward

Wow! What exposure time were you using?

I'm not sure about Televue adapters, but from Paul's photo it appears that they work like the Takahashi adapter I use which is in two parts. One ring bolts to the eyepiece and the other screws into the filter threads of the camera lens. There are three set screws on the cmeralens part of the adapter which then bolt the camera/adapter part to the eyepiece/adapter part. This eliminates the need to use the LCD screen for focusing. First focus the eyepiece without the camera in place, then bolt it on with the camrea set at infinity and you're all set. Hope this helps and isn't too tediuosly obvious.

Hal Coward

Hi Jimmy,

I have a Mewlon 180, which is comparable, and can say that the scope holds collimation very well. It is very sensitive to collimation for planetary or double star use, but if you follow the instructions in the user manual and learn to make SMALL tweaks, achieving critical collimation is not hard. I regularly split sub-arcsecond doubles (last night elongated and may have split one at 0.7" near the zenith). It will come from TNR close enough that a small tweak of the secondary adjutment screws is all that is necessary.

The one caution is that there is some mirror flop noticeable at high power double star work. I conquered this by collimating at zenith so that the deflection of the primary is small until I get to elevations low enough that the seeing is destroying things anyway. The mirror flop only becomes noticeable in my scope if I collimate using a star at low elevation and then flip the tube over.

Hal Coward

WOW! Thanks to everyone for sharing your expertise and experience. I have found it extremely helpful.

Hal Coward

Sounds like seeing was indeed the answer to your collimation concerns from the other night.

Hal Coward