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Ian.....Can you observe anything past the zenith to the North? Or is your drawing not an actual representation of the roof pitch, pier placement and all? Mike

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Yep - I was wondering that too

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Nytecam 51N 0.1W
Meade 30cm LX200+ETX-70+e-finder+C8+Ha+CaK PSTs SBIG SGS+homebuilt spectrographs
Starlight SXVF_M9+Lodestar CCDs/Canon 300D DSLR/Fuji E550
My observatory build-ETX-70 imaging-my videos

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Hi Mikey,

There is no North view unfortunately, I had a choice of North-West or South-East, so I chose the latter as it gives me better early-evening viewing towards the ecliptic.

Shortly after building the observatory & hatch, I found that I had limitations with the amount of clearance required for the C11 on top of my AS-GT EQ mount (I should have measured it better before cutting the roof!)

Also, the idea of using a hydraulic jack for extending the tripod of the AS-GT to create a variable height pier didn't really work. Even with 1/8 inch cross bracing (angle-iron) it was still too unstable with all that weight swinging from side to side.

I sold the EQ mount, to fund a used NexStar 11 GPS alt-azimuth fork mount instead, and drilled the sides of the C11 OTA to fix that mount.

The advantage of the fork mount is that it has a fixed center of gravity regardless of OTA position, so it allows me to get right up to zenith on the C11.

The tradeoff is limited exposure times for astro-photography on an alt-az, and there is no room to fit in a wedge for the C11 unfortunately.

Instead of the unstable hydraulic jack, I mounted the NexStar GPS forks on top of a Linak electric lifting column, which I can run off the 12v of the power tank no problem and is quite stable.

(More details on the Linak columns here: http://www.cloudynights.com/ubbthreads/showflat.php?Number=3400735)

I also bought two extra Linak columns, with the idea at some point in the future I'll bolt them end-to-end and create a high lift mount for my C6 OTA and a home-made wedge to get above the roofline for full 360 tracking.

That means I'll have the C11 for visual, and the C6 for longer exposure astro-photos, where the larger aperture isn't so important.... that might be a project for next year though when my funds recover!

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You might consider doing something like what I did, though my roof is flat on top.

It's a fairly heavy wood and metal 4.5' square cover riding on industrial drawer slides, so there is no need for outriggers on the roof to support the hatch. You can find pix of my setup on page 8 of the "show a pic of your observatory" thread at the top of this forum.

There was another post that sounds more like what you're talking about with a sloped roof facing south. In that case, the hatch was on rails or slides and went off to one side of the opening, like a "convertible" balcony.

-Tim.

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Where did you get the industrial drawer slides?

Finding slides long enough and heavy enough is hard.

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I didn't, initially. The contractor who rebuilt our roof after a major fire 8 years ago did. But then I was looking into a way to make a rolloff roof observatory without the outriggers, in case the building codes where I was contemplating the observatory (SW Utah) counted the outrigger space as part of the square footage. So, I looked up industrial drawer slides to see how big they come. Mine are 4 and a half feet long. The maximum size I could find was 5 feet. So, to make a decent size rolloff roof, I'd have to split the roof in two and have the sections roll away in opposite directions.

They're out there, but they're not cheap. Something like $300 each, IIRC.

-Tim.

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"We`re just waiting looking skyward as the days come down.
Someone promised there`d be answers, if we stayed around."
-Orchestral Maneuvers in the Dark, "The Romance of the Telescope"

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