ETX60/70 as a finder scope?
Posted 14 August 2012 - 09:10 AM
Let me start by saying I like to "think outside the box", but I know sometimes I just end up making things more complicated. So if this sounds too far out in left field, let me know.
I am looking for a finder scope for my 10" dob. I have a Telrad, but I would like something to go with it that give a little bit of light gathering and magnification to help cut thru the sky glow for star hopping. The basic, no base, straight thru 7x50 GSO finder is about $45, and the GSO RACI 8x50 with base is about $80.
But then I start thinking about "other options", small scopes that I could use as a finder scope, but also have the option to use as a stand alone scope, a "grab and go" for quick trips outside... The first two or three options I though of would have set me back $300-$500 (options like the Astro Tech 72mm F6 refractor, almost $400 for the OTA) Then I noticed that ETX60/70's on ebay are often going for $75-$100, sometimes with a few eyepieces or a tripod. If my math is right, one of these scopes with a basic 25mm eyepiece (that I already have) would give me about 14x, and almost 4deg TFOV. A cheap wide field 25mm would give between 4.25 - 4.8 TFOV. (the 7x50 GSO gives about 5 deg, TFOV, I think. Also, the AT72 could get to 5.6 TFOV with a 2" 35mm, 68 def FOV eyepiece, but would cost over $500 for the scope + diagonal + eyepiece)
So with the ETX60/70 - how do they unmount from the forks? My ETX90 has 4 screws, two on each fork. I can de-fork or re-install the OTA in about 5 minutes. Are the smaller ETX's the same? Also, my EXT90 has a "foot" on the bottom of the OTA that mounts directly to a photo tripod - do the smaller ETX's have this?
Last - how is the ETX60/70 as a stand-alone scope? Some places I read it has a built-in barlow? How well does that work? If you push it up to 100x-150x, how well does the image hold up? How would the ETX70 compare to the above mentioned AT72?
Any other thought on these scopes, or using the OTA from one as a finder?
Posted 14 August 2012 - 03:13 PM
Posted 14 August 2012 - 04:00 PM
Posted 14 August 2012 - 05:13 PM
How do you De-fork the smaller ETX's?
Posted 14 August 2012 - 05:18 PM
Yeah, that is not good for what I want to do with it...
Oh well... I guess I could still use it for a finder, but it would be a one way trip. Maybe I can find a cheap one on ebay with a dead mount.
Posted 22 August 2012 - 12:54 PM
I now having an ETX-70 with working goto. (ha ha!)
I keep a wide-field eyepiece in one port, and a 12mm illuminated reticle eyepiece in the other. Anything that lands in the square of the illuminated reticle is in the middle of a high power eyepiece of the main instrument.
The versatility of a flip-mirror on the ETX outweighs other conventional finders in my opinion.
As an added bonus, the Sun (and Moon) almost fill the entire field of view of the ETX-70 with a Meade LPI camera. This is great for full-disk solar & lunar images, and did a nice job on the recent Venus transit.
By the way, the above poster nytecam takes better astrophotos through his ETX-70 than I ever will with any larger scope!
Posted 24 August 2012 - 12:03 PM
NYTECAM: nice site! I see you have torn your etx down to nuts and bolts... I was wondering - I have seen a few 60/70's on Ebay with loose mirrors or broke focusers sell for less than shipping. How hard would it be to fix these? Is the mirror a glue down affair? Is the focuser screw a standard thread size?
Posted 10 September 2012 - 04:44 PM
Posted 12 December 2012 - 12:01 PM
Once the scope gets here I will probably start a new thread. Or not.