Finder scopes

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Finder scopes

Postby cwardlaw » Sat Jan 07, 2017 4:17 pm

My Celestron Evolution 9.25 came with a small red dot eye finder which has had some success bu i now feel it needs to be replaced with something a little more precise. Any direction or advice about what I might consider as an upgrade would be very much appreciated.

Thank you

C Wardlaw
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Re: Finder scopes

Postby Aratus » Sat Jan 07, 2017 5:35 pm

I think it is agreed that the standard red dot finder is badly designed with the on/off switch looking exactly like the adjustment screws, and the battery compartment making it difficult to change the battery. The viewing screen is small, and the single red dot can be obscured by a bright object. There is also a certain amount of parallax depending on the angle you look through it. However, I've yet to come across a replacement that is significantly better. A bigger screen gives more parallax. Using concentric circles doesn't obscure the target, but it does mean you have to guess where the centre is.
Looking straight through the finder means it is very easy to line it up with the sky. It can also crick your neck! Using a diagonal is easier on the neck, but harder to line up the target, at least initially.

My conclusion is that the original red dot is accurate enough with low powers to find an object in the eyepiece. I have spent money on replacements and found they cause as many new problems as they solve. I admit that I haven't tried the expensive (£100+) units.

If you want to look at the options then people I know have recommended Telrad or the Celestron Starpointer, or the Skywatcher 9x50.

The £100+ Baader 40mm Super Sky Surfer V looks interesting, but I don't have that sort of money burning a hole in my pocket :D
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Finder scopes

Postby The Man with the Corrugated Iron Roof » Sat Jan 07, 2017 11:00 pm

Skywatcher 9x50 RA. No contest! Even saw M33 through it from a dark site.
How can I be one with the universe when we don't know what 96% of it is.

My website: http://www.philippughastronomer.com/

My blog: http://sungazer127mak.blogspot.com/

Photos: https://www.flickr.com/photos/philippughastronomer/
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Re: Finder scopes

Postby Gfamily2 » Sun Jan 08, 2017 2:01 am

This time of year, when the Andromeda Galaxy / Double cluster and so much else is straight overhead, you don't want to have to crouch down to check the finderscope - or at least I don't!

I was happy to be the recipient of our Skywatcher 9x50 finderscope on Christmas Day*. It works fantastically on our 127mm Mak (replacing the standard 6x30) , and I'm getting the tools to allow us to mount it on our Meade 8" ACF scope.

*Our main present will be a Star Adventurer, which we've just ordered, and we've heard great things of from our Astro Society members.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: Finder scopes

Postby Aratus » Sun Jan 08, 2017 4:46 pm

You lot are a bunch of tempters! :D

The Skywatcher 9x50 retails at about £60, and I know several other people who have them.

I use my 'red dot' to find the initial alignment star. That is easy using the straight through red dot. (twisted neck not withstanding :o ) but how do you find a star initially using a diagonal? The field of view is 5.6 degrees, but is that enough put a star into its view by guesswork - without lining your head up against the tube? If you can assure me that it can be done easily - you might easily win a convert!
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Finder scopes

Postby Gfamily2 » Sun Jan 08, 2017 11:29 pm

Aratus wrote:You lot are a bunch of tempters! :D

The Skywatcher 9x50 retails at about £60, and I know several other people who have them.

I use my 'red dot' to find the initial alignment star. That is easy using the straight through red dot. (twisted neck not withstanding :o ) but how do you find a star initially using a diagonal? The field of view is 5.6 degrees, but is that enough put a star into its view by guesswork - without lining your head up against the tube? If you can assure me that it can be done easily - you might easily win a convert!

I agree that the initial alignment can be trickier - I'm working on that...
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
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Re: Finder scopes

Postby Aratus » Mon Jan 09, 2017 11:19 am

Let me know. If someone can come up with the design of a finder which doesn't mean at some point that you have to crank your head - they could make a mint! (How on earth I managed 45 years ago using a telescope without a diagonal I can't imaging. Perhaps teenagers have rubber necks!) I tend to choose alignment stars which are around 40 degrees in altitude. (Errors creep in if they are too low) Anything higher than that and my neck simply will not co-operate :cry:
I use an 11" Celestron SCT (CPC 1100) on an equatorial wedge, housed in a 2.2m Pulsar observatory. I use a ZWO ASI1600MC and Canon 500D for imaging.
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Re: Finder scopes

Postby Gfamily2 » Sun Jan 15, 2017 5:44 pm

Gfamily2 wrote:
Aratus wrote:...but how do you find a star initially using a diagonal? The field of view is 5.6 degrees, but is that enough put a star into its view by guesswork - without lining your head up against the tube? If you can assure me that it can be done easily - you might easily win a convert!

I agree that the initial alignment can be trickier - I'm working on that...


So, Finder assistant #1
I have a short steel tube (cut from an over-long curtain rod) that sits alongside the finderscope - currently held in place with elastics - if it works in practice, I'll try for a firmer method of attachment.
Image

Yes, it's "lining your head up", but only the same as with an RDF. Seems to align close enough using terrestrial targets, if it would only clear up at night I could tell how it works in the field.
Image

Let me know if the pictures aren't visible - I'm working off a Google Photo album, and I'm not sure sharing is set up correctly
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Gfamily2
 
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Re: Finder scopes

Postby dave.b » Mon Jan 16, 2017 12:26 am

I swapped the 9x50 finder that came with my AVX Edge 8 for a RDF just because getting the first alignment star was so damn difficult! Once you have the first star, and with a reasonable North alignment, the other alignment and calibration stars came relatively easily. After its calibrated you can happily dispense with finder.
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Re: Finder scopes

Postby Gfamily2 » Mon Jan 16, 2017 12:58 am

dave.b wrote:I swapped the 9x50 finder that came with my AVX Edge 8 for a RDF just because getting the first alignment star was so damn difficult! Once you have the first star, and with a reasonable North alignment, the other alignment and calibration stars came relatively easily. After its calibrated you can happily dispense with finder.

I find that even after alignment, the GOTO's precision isn't always great, so I like to have a decent finder, and with spectacles, getting properly lined up to use a RDF can be very frustrating.
We'll see how this sight-tube works in practice.
Scopes: Meade 8" SCT, Skywatcher 127mm Mak, Raffle winner of SW ST80
For imaging: Pentax K5, Asda webcam, Star Adventurer (new toy)
For companionship: Mid Cheshire Astronomical Group.
(Not a moderator)
Gfamily2
 
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