johninderby

It’s to do with the light path being folded and the shape of the mirrors which means the effective focal length is much greater than the physical length of the telescope.

Quote from an article on the subject.

“At first it seems that an Maksutov-Cassegrain should have a focal length twice as long as the length of the tube, since the light travels twice the length of the tube.  However, Mak-Casses actually have focal lengths about 5-7 times longer than the tube length.  This is due to the convex curvature of the secondary mirror.  This effectively magnifies the focal length, making the scope act much longer than it is “

Just measured the plug on both the SkyWatcher cable and the RJ10 cable I just bought. Colud the clone plug/socket be undersized?

16 minutes ago, Rusted said:

Thank you, John, but RJ10 plugs don't fit the motor. Nor the Skywatcher paddle socket. Too wide. I've tried.

I do like your neat set-up. A nice long belt with toothed sprockets reduce lateral tension.  Clever use of the finder dovetail too!

The RJ10 fits the Skywatcher motor as well as both the Skywatcher control box and the Hitec. The RJ11 is a bit wider than the RJ9/10 and wouldn’t fit.

Printed up a finder dovetail bar 2x as long and 1.5x taller than a regular one to mount the Skywatcher btacket on.

And this is a Skywatcher 180 mak with a 2700mm focal length.

I bought this 5m  RJ10 cable from Amazon 

https://www.amazon.co.uk/gp/product/B07NC73MPP/ref=ppx_yo_dt_b_asin_title_o04_s00?ie=UTF8&psc=1

Yes standard RJ9/10 for the motor cable and 5.5/2.1 power socket. Does come with a power lead with a cig lighter end on it but I had an AC adapter that fitted.

One of these just arrived. Quick test and it seems to work OK. It’s the new version from FLO with the seperate power cable and much stronger case.

Will be testing it out this evening..

Yes WOW indeed. Here’s another pic. Check out the step ladder need for observing. 

It’s a 42” dob. 🙀

You could always use a diagonal. There’s a pic of an 8* SCT in one of the posts in this thread with a diagonal and DSLR.

Now this is one BIG solar filter. 🙀

Hope it doesn’t need replacing too often. 😁

This is Baader’s advice.

“Before each solar session carefully inspect your AstroSolar filter for mechanical damages, broad scratches, streaks,extensive whipe marks and other quality degrading influences. Small pinholes do not degrade the eye safety or image sharpness of AstroSolar !
Hold the filter at arms length towards the daylight sun to detect dangerous defects. Small pinholes may become visible but will not be dangerous, because the light going through will be dispersed across a wide area like in a “camera obscura”. This scattered light however will cast a “hue of light” to slightly overlay the solar image information and reduce image contrast somewhat.”

The XX Large will fit the C5

http://www.lenscoat.com/lenscoat�-hoodie�-large-p-386.html?osCsid=3c40c42c2adc3963d771c4ce772ce010

I use one of the Lenscoat Hoodies on Big Red.

Camera Take 2 😁

Bought an Altair GPCAM3 290M last week and when testing it was so underwhelmed by it I sent it straight back. Maybe it was just a defective one? 🤔

Anyway then I ordered a ZWO ASI290MM. More expensive than rhe Altair but hopefully will perform as expected. 

The tube clamp screws directly to the mount and isn’t removable although can be opened to fit the OTA.  To change OTAs you would need to replace the complete two part clamp. Finding the new size clamp would be the problem. These scopes date from about 2000 so getting parts is a bit tricky. 

This mount doesn’t come with a dovetail type mounting arrangement for the OTA but a moulded two piece tube clamp so you have to replace the whole tube clamp. If you could find the clamp assembly for the 130 then you should be able to change to a 130 OTA. 

https://s3.amazonaws.com/celestron-site-support-files/support_files/1228334587_nexstargt.pdf

10 minutes ago, Mark at Beaufort said:

John I noticed that you changed the finderscope bracket. I assume the old bracket are simply held by screw bolts with no nuts to worry about falling inside.

Yes it was a simple bolt on. However the rear dust cover that the bracket fastens onto is plastic so very, very easy to strip the threads which happened to me so I tapped the holes out to the next larger size. Would be asy to loosen the dust cover and put nuts on the inside though.

BTW there is a proper metal back plate on the scope under the dust cover.

Motorising a Skymax 180 Focuser

Fitting a Skywatcher Autofocuser turned out to be a simpler job than expected. 

Printed a finder dovetail out but doubled the length from standard. Then took one of the mounting bases than came with the focuser unit and flattened the main part of it in a vice so that it would sit flat on top of the dovetail. Drilled an extra mounting hole and countersunk the hole so the bolt heads wouldn’t protrude.

Now I had the motor unit ready to fit into a standard Synta type finder shoe.I added an extra mounting shoe to the existing mounting holes in the scope. Originaly intended so you can fit the finder in another postion.

Used GT2 toothed drive pulleys. 20t for the motor and 40t for the focuser knob which gives a 2:1 ratio. The 20t pulley had a 5mm bore that needed drilling out to 6mm to fit the motor shaft. The 40t pulley had a 12mm bore that needed drilling out to 13mm then a bit of filling to enlarge the the bore to 13.15mm.  Had an old AstroEngineering badge that was just the right size to fit the pulley and cover the big hole in the pulley. Not really necessary but looks neater.

Temporarily using a 280mm drive belt as that was readily   available. A 270mm is on it’s way but takes a few days to arrive. Runs very smoothly and is easily removable and the drive pulley makes a nice focuser knob.

HitecAstro DC Focus V2

Could come in handy for motorising a focuser. 😁

Focuser knob

Wanted a bigger focuser knob for the scope and had a spare GT2 60 tooth drive pulley and thought it would make a good focuser knob. The focuser knob simply would not come off so had to resort to cutting the old knob in half with a cutting disk to get it off.

The drive pulley had a 5mm bore which was close enough to the shaft diameter of 4.72mm. The drive pully was intended for a 10mm wide belt.

New knob works perfectly and makes focusing easier. 

Plus counterweight bar and weight 😁

Here’s a thread on CloudyNights discussing it. 

https://www.cloudynights.com/topic/608590-synscan-upgrade-kit-for-bresser-eq5-mount-compatibility/

How about the Skywatcher AZ-GTi WiFi mount which can also be used in EQ mode. Compact and light weight but would handle a 70mm scope.

The Televue Powermates are excellent but the Explore Scientific equivelents are 95% as good but much, much cheaper and well worth considering.

 https://www.firstlightoptics.com/explore-scientific-eyepieces/explore-scientific-2x-3x-5x-barlow-focal-extender-125.html

Don’t think this was a legal drone flight but mostly distance shots anyway.