Concerns with generic finderscope

Manav (Yugant) · #1 15-09-2009, 01:43 PM

Hi Everyone,

I have a generic finderscope which came with the skywatcher reflector 254mm. I have been really struggling with a couple of things as highlighted below:

1. Using the GOTO mount the finderscope ends up in awkward places and my neck takes a battering.
2. For visible stars/planets its easy for me point to the middle crosshair and move to the OTA for the splendid view but if I want to track or locate DSO its like looking for a needle in a haystack since the image is hard to distinguish made worse by the reverse direction.
3. The crosshair is a pain to see and my eyes end up hurting. I usually move away from the finderscope and to see if I’m pointing to the correct direction.

The questions I have is; what is the difference between using something like a Rigel Pulse Guide illuminator on a Stellarvue finderscope and a red dot finder commonly available at BINTEL. The stellarvue looks impressive but its quite expensive are their any other alternatives please share your experience.

Take Care and wishing clear skies.

[1ponders] (Paul) · #2 15-09-2009, 01:50 PM

There is just no comparison with the Stellarvue with illuminated finder. I wouldn't be without mine. To make things easier in the mean time, you could go for a standard right angle finder and hold a red torch so that a little bit of light enters the objective of the finderscope. It makes the X hairs stand out really well. Alternatively you could drill a hole in the side of the dew shield and fit a red LED (with suitable adjustment control) in the hole. someone here did it with great results apparently.

many DSOs are too faint anyway to be seen in the finderscope. Star hopping is the usual way around this problem.

Manav (Yugant) · #3 15-09-2009, 01:54 PM

Thanks for such a quick reply! Any ideas where I can get the cheapest one in Australia or overseas (not sure if they would post one out). The only place I could locate them is www.sdmtelescopes.com.au and the price is a bit hefty.

TC

toryglen-boy (Duncan) · #4 15-09-2009, 02:21 PM

Quote:

Originally Posted by Manav

Thanks for such a quick reply! Any ideas where I can get the cheapest one in Australia or overseas (not sure if they would post one out). The only place I could locate them is www.sdmtelescopes.com.au and the price is a bit hefty.

TC

you might be cheaper getting something like a RA correct image finder from Andrews, for around $70 - $80, then fitting the LED. you can buy them quite cheap, that place in HK has them dirt cheap,

http://www.tan14.com/gears.htm

[1ponders] (Paul) · #5 15-09-2009, 02:22 PM

I bought mine from www.optcorp.com They are great to deal with and if they have the item in stock it can often be here within a week. Just check with them first if they have them in stock.

there is their 80mm one http://www.optcorp.com/product.aspx?...5-166-168-9776 which is backordered.
their 60mm
http://www.optcorp.com/product.aspx?...5-166-168-9775 though low in stock
and their 50mm
http://www.optcorp.com/product.aspx?...5-166-168-9755

I have this one with the rotating eyepiece end
http://www.optcorp.com/product.aspx?...5-166-168-8503 but you need to order the illuminator with this on and the finder is on backorder

Just check with them first

ps check to see if they come with the finder bracket or if they will fit your standard finder bracket

the accessories page
http://www.optcorp.com/product.aspx?...-168-8503&tb=5

Manav (Yugant) · #6 15-09-2009, 02:43 PM

Thanks for all the info! I'll check the Skywatcher finderscope brackets when I get home.

TC

astro744 · #7 15-09-2009, 08:26 PM

Welcome to the wonderful world of EQ Newtonians where the finder and eyepiece are often in awkward positions.

You mentioned the image is reversed but I'm looking at the SW photo's and they show a straight through finder. This type has no mirrors and therefore the image cannot be reversed but will be be upside down although the angle at which you hold your head can rotate the image. For mirror reversal you need an odd number of reflections, eg. 1,3,5..

May I recommend a Telrad to start with until you get used to your finder. I personally find an illuminated finder more annoying than a non illuminated one and I can also do without the crosshair. I have tried the pulse guide and it was very distracting and I could not concentrate on seeing the object in the finder. This was on a Stellarvue F80M. I now use a 20mm Plossl but have tried a 16mm T5 Nagler which is a truly wonderful combination giving 19x mag at 4 degrees (matching the outer circle of a Telrad). For better edge performance, Stellarvue recommend a highly corrected eyepiece such as a Nagler for the F80M since it is f3.75. The Stellavue wide angle eyepiece that the pulse guide can connect with does not have the same edge performance as a Nagler does. This all makes for one expensive finder but I have found the F80M works very well with a low cost 20mm Plossl.

You may also consider replacing your straight through finder with a Right Angle Corrected Image (RACI) 8x50 finder which is not too expensive. However depending on the angle of the telescope the RACI may be more inconvenient since you may have to rotate the finder within its rings to look through it properly thereby losing finder collimation with the main 'scope. This is why the straight through is offered on the EQ Newtonians. The RACI is better on the Dobs.

If you get a Telrad and a very low power 2" eyepiece (highly corrected will be better but expensive), you may get away without needing a finder. You can try a 30mm/80deg eyepiece that will give you 40x at 2deg true field which matches the middle circle of a Telrad. With this combination you may find going from Telrad to main 'scope is all you need. I used this combination for many years until I got the F80M for those barren areas of the sky.

Note though there are many cheap 30mm/80deg eyepieces on the market and most if not all will exhibit severe curvature of field and other abberations in the outer 30% of your field in a 1200mm, f4.7 telescope. A Paracorr corrects for mirror coma and also helps with curvature but again is expensive.

Manav (Yugant) · #8 15-09-2009, 10:46 PM

astro744 - Thanks for such a detailed response; I had just emailed optcorp sales team to get the check on postage and handling of Stellarvue F50M to Australia.

Was just reading up on the Telrad reviews so I could understand how they work. I am still leaning towards the F50M solution as I can always pull it away down the track when I can afford to get a SCT

Will see how all this pans out in next few days.

Thanks again guys!

astro744 · #9 16-09-2009, 09:51 AM

If you can afford the F60M go with it for a bit more aperture and magnification (more stars!). It is still very lightweight at 23oz compared to 19oz for the F50. An extra mounting foot is helpful too if you want to move between different telescopes but you can always get an extra one later. If you want a white finder then the F50W is the go as the 'M' series are matt black. I'm not sure if the F60 is available in white.

I would recommend buying locally as I don't think you'll save any going direct and may even cost you equal or more with freight. SDM are a dealer and I think their prices are quite reasonable. Their service is certainly exceptional.

You will find you will end up adding a Telrad too since it is a pointing device and quite useful especially if you use a right angle finder.

bmitchell82 (Brendan) · #10 16-09-2009, 11:20 AM

I find even the most faintest of DSO's with my 9x50 finderscope (i have the same scope as you). Whats the trick to using any finderscope well?... Using both eyes.! its weird to get used to but once you get your head around it finding things will just happen. i was lucky as a child my old man taught me how to shoot guns with 2 eyes open. Same principle, one eye on the target and one eye on the field. the illuminated cross hairs arnt much use anyhow as even at a low brightness it will drown out any faint stars. Also using this method is exactly like using a Telerad, as your brain can combine the images from each eye and tell you when they are overlaying. and the eye with the finderscope can see what it is you want to point at (unless its too faint).

Using a star map and a suitable circle (thats the hard bit getting what your finderscope sees) which represents your FOV (SW finders are i belive 5 deg) then look for star patterns and match them to your FOV, i ran a Messier marathon like this even when my goto went on the blink i still found majority of them untill the clouds came over.!

Good luck with what ever you choose.

Manav (Yugant) · #11 17-09-2009, 11:06 AM

Quote:

Originally Posted by astro744

You will find you will end up adding a Telrad too since it is a pointing device and quite useful especially if you use a right angle finder.

Took your advise will be ordering from SDM as the OPTCORP guys never replied back to my query (and I feel like supporting local businesses). I'll be getting the F60M with the brackets. Hopefully one day in the not so distant future when I get a SCT I'll just migrate this across. I'm still reading up on the TELRAD and will consider that down the track hopefully the F60M will fill that massive gap.

On a side note I really am impressed with the quick and detailed responses in the ICEINSPACE forum. You guys have a good community here, providing good support to beginners. Thanks Guys.

bmitchell82 - Sorry to hear about your GOTO what happened?

bmitchell82 (Brendan) · #12 17-09-2009, 11:37 AM

there where too many people using the power at the site i was at, EQ6 mounts are sensitive to power and will start to play silly buggers if not supplied with a constant voltage >12 Volts.

astro744 · #13 17-09-2009, 02:25 PM

Excellent choice of finder and I'm sure you will enjoy using it very much.

If you can get to a star party have a look through a Telrad as there are bound to be a few at any star party. As I mentioned before it is a pointing device and is very useful on any telescope. It's outer circle is 4 degrees and is a nice match the the F60M which has as standard a 23mm/50deg eyepiece giving you a true field of 5deg at 10x power. Very nice indeed!

If you ever want more power you can use any 1.25" eyepiece, but you just wont have the crosshair. I've tried a few different combinations on paper and a 14mm Radian will give you 3.7deg at 16x with 3.7mm exit pupil and 20mm eye relief. Wow! A 20mm Plossl would give 4.4deg at 11x and 5mm exit pupil and a 15mm Plossl would give 3.2deg at 15x and 4mm exit pupil but not a lot of eye relief.

Anyway, enjoy your new finder!

Ian Robinson · #14 17-09-2009, 02:50 PM

For eyepiece positioning .... nothing beats tube ring/clamps , you can loosen off the clamp bolts a tad and rotate the tube to get a more comfy eyepiece position.

Check out Orion Optical UK (http://www.orionoptics.co.uk/) who do custom tube rings attached to a dovetail and spacers ,all they need are your accurate tube OD measurement and they'll be only too happy to quote , and you can buy direct from them.

Lumicon have nice 50mm and 80mm finderscopes which are straight through or right angled , and they are cheap too, and you can buy direct from them.

This is what I plan on putting on my upgraded newtonian : http://www.lumicon.com/telescope-acc...Finder+Body&hn= + http://www.lumicon.com/telescope-acc...racket+80mm&hn= as I already have the 25mm Xhair and a couple of spare 1.25" stardiagonals.

I don't think my old 50mm Lumicon finder will cut it on the newt .... but might be OK as the finderscope for my CG5 camera platform , the old 60mm Tasco achromat (white tube 1960s vintage) which I'm rebirthing as my CG5's guidescope only has a 30mm finderscope which is WAY TOO TINY .....

You can convert straight through finderscopes to right angled finderscopes , just need to shorten the tube to make allowance for the extra pathlength through the star diagonal.

Manav (Yugant) · #15 18-09-2009, 04:52 PM

Just a quick update - I was communicating with SDM via email on the pricing and they were apparently overstocked on F80M. I managed to get a deal with F80M + Brackets + Rigel PulseGuide Illuminator for 350AUD incl postage

Should be here on Monday - I'll review it to let you guys know how it turns out.

astro744 · #16 18-09-2009, 07:44 PM

Quote:

Originally Posted by Manav

Just a quick update - I was communicating with SDM via email on the pricing and they were apparently overstocked on F80M. I managed to get a deal with F80M + Brackets + Rigel PulseGuide Illuminator for 350AUD incl postage

Should be here on Monday - I'll review it to let you guys know how it turns out.

Great deal! Thats' about the US price when you add it all up.

Note though it is a lot heavier than the F50 or F60 at 2.5 pounds (1.1kg) compared to 23oz (0.6kg) for the F60M. You may have balance issues on your telescope as I have with mine. However I have added a counterweight at the bottom of my tube and absolutely love the F80M since it can pull in very faint objects including numerous galaxies.

However, I did not like the SV wide field cross hair eyepiece and pulse illuminator (in fact very much disliked it). I found the edge correction was poor in the wide field but the annoying pulse was what I couldn't stand as it was very distracting and I couldn't concentrate on what I was looking for. I did have a wide field 70 deg and not the standard 50deg SV eyepiece and I think the 50 deg would be much better at the edge.

Stellarvue recommend a Nagler (or other highly corrected eyepiece) and I tried a 16mm T5 and WOW! 4 deg at 19x and sharp to the edge! However I mostly use a 20mm Plossl giving me 3.3deg at 15x.

I'm sure you'll enjoy your new finder very much.

Manav (Yugant) · #17 18-09-2009, 11:09 PM

Quote:

Originally Posted by astro744

Great deal! Thats' about the US price when you add it all up.

I know and all thanks to you

I'll try to stick generic eyepiece at the moment and see how it all pans out before jumping into the deep end.

Can't wait till Monday!

-Off topic rant- Why is it always cloudy on Friday evenings?

[1ponders] (Paul) · #18 20-09-2009, 02:27 PM

Quote:

Off topic rant- Why is it always cloudy on Friday evenings?

'cos you just bought a new Astro Goodie. Wait and see what happens when it gets to you.

Manav (Yugant) · #19 20-09-2009, 06:00 PM

Australian Government Bureau of Meteorology
New South Wales
SYDNEY FORECAST
Issued at 3:45 pm EST on Sunday 20 September 2009

Forecast for Sunday evening
A shower or thunderstorm. Light to moderate westerly winds and
coastal seabreezes.
Precis: Shower or thunderstorm.

Forecast for Monday
Cloud increasing in the afternoon with the chance of late showers.
Light to moderate southwest to southeast winds tending northeasterly
in the afternoon and freshening near the coast later.
Precis: Mostly fine. Cloud increasing later.

Its similar for Tuesday too!

mithrandir (Andrew) · #20 20-09-2009, 06:29 PM

We've already had one hailstorm. 10mm in 5 minutes.