GSO Finder scope cross hairs disappointment

[Dennis G]

The GSO right- angle finder scope is disappointingly inaccurate as far as the cross hair arangement set-up goes. The eye piece being 20 mm in diameter permits the entry of sight to be any where with in it making the actual cross hair alignment inaccurate. To over come this I've placed a black disc with a 3 mm central hole over the eye piece which helps but doesn't provide the complete answer. In a gun sight finder the cross hairs are etched on clear glass and possitioned within the optical arrangement so that regardless of eye movement the alignment remains accurate.
Has any one pulled a GSO finder scope down and made successful improvements to the accuracy?

[ving]

i too noticed this when i got mine...

[Starkler]

Why is this a problem? I have never had any issue with putting an object into the field of the highest mag eyepieces after having aligned the finder properly in the first place.

[ving]

its not a problem. ts jut something i noticed... move ya head around and the hairs move too...

[Kevnool]

Never taken much notice but i bet i will now.

The crosshairs are so thick ,shame they were`nt like looking through a rifle scope (thick & thin)....cheers Kev.

Actually does any one use a rifle scope as a finder :confuse3:...cheers Kev.

[mrsnipey]

I noticed this with my Skywatcher illuminated finder I got with my ed80.
My GSO finderscope for the dob doesn't do this (it's not illuminated and it's a straight through).

I found it annoying at first as I was never sure if the star had drifted or if I had put my eye in a different place while drift-aligning. I'm used to it now though and it's not a problem.

I looked at the rifle scopes on ebay but they were all 30mm or less. Wouldn't be ideal for finding those dimmer stars while hopping around.

[GrahamL]

I always found my gso RAF fairly usable as is ..but crosshairs or not
it sure wasnt a sharp focus..as for modifying it ?...you would be trying to make a silk purse out of a sows ear imo.

my sparrowhawk is great and I can recomend it as a big step up
for a fairly cheapish finder..The ability to focus has had me remove the crosshaired eyepiece from it as I think it spoils the view .They do make
some handy acceseries for them as well.
http://www.cloudynights.com/item.php?item_id=1324

cheers graham

[Dennis G]

It is great to have so many replies. The GSO finder that came with rhe telescope has an eye piece lens with a diameter of 20 mm in a vertical holder 50 mm in total length, right angles from the line of sight. The cross hairs (wire) are attached to the bottom end of this tube. Using Planet Jupiter as the target and assuming you have centred the planet in your telescope using a 9mm eye piece and to the best of your ability have the planet under the cross hairs, which will only be accurate to the centre of the eye piece lens. The smallest movement of the eye off that centre line moves the planet. Set up the CCD imager and computer. Put the cross hairs over the image and see if the planet is on the computer screen. Even a disc with a 2 mm hole to line up the cross hairs and object, which reduces eye movement considerably, but still allows a huge error to occur isn’t the answer. I carelessly used the term gun sight in my submission, whereas I should have explained fully the sight I have is ex military gun not a rifle. It is used as a surveying level and has a reasonable field of vision, but the point I wish to emphasize is, regardless of eye movement the cross hairs and object remain aligned and most of all the cross hairs remain within focus with the object. I agree you get what you pay for be it a pig’s ear or such, but I had hoped ans still do, there's a knowledgeable member of IIS who has overcome this inaccuracy and is willing to pass on his knowledge.

[Satchmo]

Dennis

I have one of these finders and mine works perfectly. I can't find any flaws in mine and I've owned a number of finders.

The fact that the star seems to move about on the cross-hairs as you move your head is because it is not quite in infinity focus and you are using your eyes natural accomodation ability to bring it into focus. Undo the nurled ring behind the objective cell, and screw it right back. Spin the objective around until you get a sharp focus with your eyes relaxed. As you are focussing look up at the skies ocassionally naked eye to make sure your eye is at a distant accomodation as you focus the finder. You may be surprised at how far you have to move the objective. Finish by screwing the knurled ring back up against the objective cell.

Don't expect too much from an 8X scope though. Expecting to get a planet on a small CCD chip is probably expecting too much.

[kinetic]

Yes Kev I do, on my 8" Newt.
It's a 4x riflescope...crosshairs are beautifully crisp at infinity focus and
no mentionable image shift that has been described in this post.
(although it seems a member has posted a solution).

4x is a little too low and it's only a 20mm objective so it's a bit
poor for deep sky star fields.
My GSO 12's finder is a breath of fresh air as far as finders go
I love it. It is a perfect field and orientation ( Right angle correct image).
When i swivel the RA it doesn't change the alignment noticeably either.

regards,
Steve B.

[Kevnool]

Thx Steve i may invest in one just to see...cheers Kev.

[Craig.a.c]

I've only had the pleasure of using mine for about 5 mins when I got it, seems to be ok though. Took me a while to realise that you can focus the finder scope though. The instruction booklet that came with scope wasn't the most informative read I've had.

[GrahamL]

:whistle::whistle: Me to I had my scope a year and a half ,sold it a year back
and am just finding out now:P..I was wondering if mark was talking about the same finder .
I really must change my approach to instruction booklets ....by reading them :)

[Satchmo]

All the GSO 8 X 50 finders use the same objective focus system, in fact its generic to most other brands and types of finderscope too.

[Dennis G]

Thanks Satchmo, I appreciate your comments and I'm sure many others who read it will also. It will be put to the test next clear evening.
A question for the Iceman and all who have read his helpful comments regarding my pictures ex DMK 21.
I'm sure the fault was caused by over sharpening Mike, so I'm including the picture again for further comment. I reprocessed it and took care not to extend the sharpening.
If the AVI is saved in Bitmap does it make the details sharper?
Is it possible to capture a star cluster with the DMK imager? Such as doubling the number of frames or changing the exposure?
The attached picture has been cropped from the full size and cannot be enlarged