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areyouabus
14-09-2017, 05:28 PM
Hi all, hoping someone has done this already.
I have been struggling to find faint galaxies using my current generic 9x50 finder scope so am looking at upgrading to an ST80 which can also be used as a travel/kids scope.

Just wondering how i can best mount it to my 8" collapsible dob so that it can be still taken off easily?
Getting 80mm guide scope rings (like the ones at bintel) and then some kind of mount to then attach through the finder scope dovetail seems like the best way without drilling new holes.
I have tested having 2kg extra at the top and it doesn't seem to affect balance much.
I have thought of using a large aperture finder scope but these all seem to have helical focusers which turn the eyepiece in a right angle diagonal.

thank you for any assistance!

rustigsmed
21-09-2017, 09:09 PM
hmmm tough one, is it going to be too heavy when you're away from zenith? i think the best way is to be checking star maps and star hop - just concentrate on getting the finder and newt well aligned.

Wavytone
21-09-2017, 09:32 PM
Hi Pauly,

IMHO there is a much better alternative - ditch the idea of a big finder and instead equip your mount with encoders, a Nexus II (from Astrodevices) and use Sky Safari to show where your scope is pointing - very accurately. With this on say an iPhone or iPad you can reliably push the scope to anything you choose in Sky Safari and put it in the main scope field of view every time. This will cost about $500-600 depending on your scope and the parts needed. There is also a setting in iOS to set the screen deep red, system-wide, so it won't destroy your dark adaptation, yet remains surprisingly readable.

See example below. Once you have used a push-to scope with a heads-up display like this, I can guarantee you won't be interested in big finders. But if you want to stick to an old-school big finder... two considerations - Where to put it, and how to mount it.

On a dob there are some choices IMHO if you're prepared to step away from the scope eyepiece - a finder doesn't have to be up the top.

The first that always appealed to me is on the side of one of the altitude axis, as this won't affect the balance of the OTA if yours moves freely. If yours is stiff... maybe not relevant to you.

The other place is at the back end, on top of the mirror cell. Might seem daft but many is the time I have resorted to simply getting down under the arse-end of a dob and simply sighting down the OTA because some poor dill cant figure out how to align a hopelessly small finder.

As for how to mount it there are basically two approaches:

1. Rings, as you know, on a short Vixen or Losmandy rail. Large ugly and fragile, and will probably damage the paint job on the scope if its a nice one.

2. If the scope has a mounting "foot" of some sort, then you could use an XY adjustable base. There are a few:

Simple one:
http://www.rothervalleyoptics.co.uk/geoptik-x-y-guide-mount.html

(Vixen makes something similar)

Or these beasties:

https://www.aliexpress.com/item/S7974-medium-low-center-of-gravity-micro-PTZ/1971192613.html?spm=2114.10010108.1 000010.4.4b24ae2bdpC6Xb&traffic_analysisId=recommend_2056_n ull_null_null&scm=1007.13438.37934.0&pvid=d76dabb3-6e88-4e3f-a05f-c55d2709771f&tpp=1

https://www.aliexpress.com/item/S8177-2-Stronghold-Tangent-Assembly-set/32822479423.html?spm=2114.12010108. 1000023.3.7d847a7te6pJN

ADM and Losmandy made a couple too.

areyouabus
23-09-2017, 06:54 PM
Thanks for the ideas. I use sky safari already with my telrad, maybe i just have too much light pollution for any fuzzys higher than 7 mag. The day someone converts an autoguider into a push to service, they will make a lot of money.
The encoders sound good but cost nearly as much as upgrading to a goto mount.

For now i might have to look at an orion 70mm multi use finderscope and permanently keep my panoptic in it. Or invest in the widest fov eyepiece like a 42mm gso superview.

Thanks again!

Boozlefoot
30-09-2017, 07:27 AM
Skywatcher Star Adventurer latitude base, available as accessory $89.00. Simple adjustment to align with main scope, carries 80mm Mak with ease. Works for me quite well, especially with the illuminated reticle.:) (Pretty sure it will accept your Orion dovetail for quick release) My grandson also likes it because he can view through the Mak while I'm using the dob and we can discuss what we're seeing!