25x90 Super Finder

[johninderby]

25x90 Super Finder

I picked up this Star Sky 90 achromat refractor for £60.00 from Scopes'n'Skies recently..The scope was in perfect condition except for the optics that were really filthy. After cleaning a few times with Baader Optical Wonder Fluid they came up very well..The optics were actually in good shape under all that filth .The Star Sky 90 is a nice light weight refractor with a very smooth rotatable single speed 2" Crayford and a retractable dew shield. The optics are nice and sharp with well controlled CA. The scope would make a great travel scope for anyone on a budget, however I had in mind using it as a super finder on a 14" dob when I purchased it.

Star Sky SS90 Doublet-achromat

Fully-multicoated objective lens

Aperture - 90mm

Focal length = 500mm

Focal Ratio - f/5.5

2" Crayford focuser,rotatable, 90mm travel

OTA weight 1.9Kg

I bought a pair of ADM 125mm guide scope rings and fastened them onto a short solid dovetail bar and then bolted a dovetail saddle from a Skytee 2 mount "upside down" onto the bottom of the solid dovetail bar. Easy to do as there is a long slot in the dovetail and so just a couple of bolts right trough the lot. I fastened a Skywatcher medium dovetail to the OTA. Now the Skytee saddle slides along the dovetail bar on the OTA. Simple but effective and solid. See there is a use for the standard Skytee 2 saddles after all.

I added an Omegon 90 degree 1.25" erecting prism diagonal and my Orion 20mm 70 degree illuminated reticle eyepiece. The diagonal is very well made and has a brass compression ring. Initial tests show it performs well both for terrestrial and astro use at low powers, and of course for it's intended use in a erect image finder. As the set-up is fairly light I only had to add a small counterweight to the bottom of the 14" dob to get it to balance.

Staring to look a bit crowded at the top of the OTA now what with the new "finder" as well as the Telrad and the StellarCAT control pad and the SkyCommander control box.

John

PS

Would make a great guidescope as well wouldn't it.

[russ]

wow that certainly trumps my 65mm finder effort. Looks the business John. That was a great bargain from Astroboot. My dob mod all looks a little below par compared to your scope. Now that would be a dream scope for me!

[michael.h.f.wilkinson]

Neat, also trumps my 16x70 finder (that uses a 22mm 70deg FOV illuminated reticle EP). If the FOV is a bit narrow, you could use some cheap focal reducer. A 0.8x would yield 20x magnification, and 3.5 deg FOV.

[johninderby]

Neat, also trumps my 16x70 finder (that uses a 22mm 70deg FOV illuminated reticle EP). If the FOV is a bit narrow, you could use some cheap focal reducer. A 0.8x would yield 20x magnification, and 3.5 deg FOV.

Good idea about the focal reducer. I've got an Antares 0.5x 2" FR that should give about 0.6x when placed on the 1.25" to 2" eyepiece adpator.

John

[Telrad]

Star Sky SS90 Doublet-achromat looks great!

[swamp thing]

Hi John

Now that's what you call a finder.

Gonna have to get something similar for my bigger Dob.

Regards Steve

[Peter Drew]

Any balance issues?. .

[johninderby]

Any balance issues?. .

The "finder" is pretty light so it's not been a problem. Just had to add a small extra counterweight to the OTA. Of course with the OO dob being mounted with tube rings I can also just slide the OTA down a bit for balancing if needed.

John

[Moonshane]

Looks superb John - really snazzy!

I bet this makes finding the faint stuff a lot easier

[johninderby]

I bet this makes finding the faint stuff a lot easier

That's the theory anyway.

John

[spaceboy]

Very nice John. Like the Baader focuser also!!!