Officina Stellare Veloce RH 200 2nd Light Report

[Harel_Boren]

Here's the 2nd light report I have previously posted on CN and SGL.. I hope you all find it interesting and of use...

This is the 2nd time in the field – I had spent the night at Tal Faibish's place in Eilat (the very southern tip of Israel, where the boarders of Jordan, Israel and Suadi-Arabia nearly touch), and this allowed us to reach our desert location by 5pm, and start of imaging at 6:30pm.

Our location

My son Ben, who accompanied us that night, shot several images, including panoramas, of the place.
Though it's desert, you are able to see the snow-covered mountain tops in the Jordanian side of the boarder, a few miles away.
I know it may look like "Curiosity images of Mars" to some of you, but no … - it's the Israeli Negev Desert http://www.cloudynights.com/ubbthrea...ns/roflmao.gif

Panorama #1: http://www.pbase.com/boren/image/148323020/large (you may like to press "original" under the image, and get a hi-res view… It's lovely).
Panorama #2: http://www.pbase.com/boren/image/148323021/large
And the snow covered mountain tops: http://www.pbase.com/boren/image/148323022/large
With some images of the sun rising on the desert road, on the way back: http://www.pbase.com/boren/image/148322997/large and http://www.pbase.com/boren/image/148322999/large

The setup

We didn't bother the ASA DDM 60 for the Veloce that night, but simply used the NEQ6 with guiding.

We've used a paper-made dew shield for the guiding scope, and an off-the-shelf dew heater for the Veloce RH 200.
You can see images of the setup, as it was still pointing to Ursa Major, at the end of the night (temperature: -2 C degrees):
http://www.pbase.com/boren/image/148323004/large and here: http://www.pbase.com/boren/image/148323006/large

Focus / Bahtinov Mask Focusing

We used a pre-prepared Bahtinov Mask, which we've prepared to spec (focal length, etc.) and had laser cut from fiberglass.

We tried focusing without a motor focus, using the Bahtinov mask, and we find it near impossible to reach the required +/- 20 micron zone, which is the calculated Critical Focus Zone (CFZ) for this short focal length telescope.

With the motorfocus is was a walk in the park - took us about 60 seconds to reach perfect focus (+2.6 micron) measured using Bahtinov Grabber, on Sirius.
The focus was finished at 18:30, and after guiding was set up (using PHD) the first actual object 10 min. frame came in at 18:46.

Focus was sustained, with no change, till the last frame came in at 04:02 in the morning. The temperature change during this 10 hour stretch was ~ 14 C degrees (from ~ +12 C down to ~ -2 C).

Here's a one-minute image, with its respective measured roundness and FWHM: http://www.pbase.com/boren/image/148384113/large

Astrodon Gen II filters parfocal performance

These filters proved to be PERFECTLY parfocal. No focus change was done or required while changing from color to color and from color to luminance. Astrodon filters is one of the purchases I just keep being happy about time and time and time again. http://www.cloudynights.com/ubbthrea...emlins/bow.gif

Field Flatness

We can actually say nothing here, except that the scope delivers a perfectly lit and flat field, across the whole frame of the SBIG ST 8300.

No flats were employed to create this stack of twenty two 10 minute frames, and the measured flatness graph which was done on a random one is pasted to the top-right of this image.

http://www.pbase.com/boren/image/148384163/large

Summary
All in all, the Powernewt has gained a worthy brother with which it will, alas, have to part of our planned long imaging trips abroad (as the Veloce is more compact and easier to travel with). http://www.cloudynights.com/ubbthrea...mlins/jump.gif
Looking back, this is a lot of hassle considering that our Southern-Hemisphere imaging location in the Kalahari (Namibia) has some pre-fit imaging scopes at hand, which one can use from a cozy warm room just underneath their dome. However, we both find no fun in using someone else's scope, on someone else's computer, using someone else's camera and someone's preset SW http://www.cloudynights.com/ubbthrea...mlins/cool.gif

Quite crazy, wouldn't you say? ... But isn't this whole hobby a crazy endeavor for people (just a little) out of the right minds? http://www.cloudynights.com/ubbthrea...lins/smile.gif

Cheers,
Harel

[MrB (Simon)]

Hi Harel,
Nice scope and an interesting read.
Thanks for posting

[alistairsam]

Hi Harel,

That sounds like a nice adventure and great results.
But how on earth did you get that car in the pit?
Also, slightly off topic, could you tell me what the reduction ratio is for the focuser stepper motor gearbox? I believe that is a mclennan gearbox.
Did you have issues with tilt due to any camera flex or did it just work.
Also, one suggestion would be to have a 1024 px height image to view the panorama as otherwise it doesn't fit in a 1280x1024 monitor.

Cheers

[dvj (John)]

Today I ordered a 3nm bandpass filter for the RH200 f/3. We'll see and attempt to measure the actual bandpass shift at these fast focal ratios.

jg

[dvj (John)]

I can't imagine not doing flats. Here is my CCD Inspector view with the STL11000 and my RH200. The RH200 f/3 has a curved field. Filters have different transmission characteristics and dust motes, not to mention the telescopes optical system. Bottom line; I would always do flats for the best from my images.

[avandonk]

Originally Posted by dvj

I can't imagine not doing flats. Here is my CCD Inspector view with the STL11000 and my RH200. The RH200 f/3 has a curved field. Filters have different transmission characteristics and dust motes, not to mention the telescopes optical system. Bottom line; I would always do flats for the best from my images.

I find it rather miraculous that the non flatness of the RH200 seems to be regulated by your sensor geometry. If it was optic based it would show circular symmetry not quasi rectangular.

Does your sensor have microlenses? I bet it does!

The RH200 has a flat field even far better than specified.

http://d1355990.i49.quadrahosting.co...R_HA_NII_L.jpg

Bert

[Peter.M]

John's CCD inspector image is interesting indeed. It would imply that rotating the camera 90 degrees would make the sides of the image worse. That is something that I can not believe.

[dvj (John)]

Originally Posted by avandonk

I find it rather miraculous that the non flatness of the RH200 seems to be regulated by your sensor geometry. If it was optic based it would show circular symmetry not quasi rectangular.

Does your sensor have microlenses? I bet it does!

The RH200 has a flat field even far better than specified.

http://d1355990.i49.quadrahosting.co...R_HA_NII_L.jpg

Bert

The KAI 11000 is an interline CCD with microlenses

My point was that flats should not to be ignored. That CCD Inspector image was of multiple test images taken without a flat subtracted. That's what my raw field shows with my STL 11000

An 8300 array is significantly smaller in field coverage. Obviously covering the inner portion of the image circle, nowhere near the edges of the 42mm image circle.

jg

[Poita (Peter)]

Originally Posted by alistairsam

Hi Harel,

But how on earth did you get that car in the pit?

Also, one suggestion would be to have a 1024 px height image to view the panorama as otherwise it doesn't fit in a 1280x1024 monitor.

Cheers

Bugger that, just get a better monitor

But yeah, how did you get that car in there?

[cventer]

"Focus was sustained, with no change, till the last frame came in at 04:02 in the morning. The temperature change during this 10 hour stretch was ~ 14 C degrees (from ~ +12 C down to ~ -2 C)."

I have to say I am somewhat skeptical of this claim. Bert another Rh200 user on this forum has gone to great lengths to control the temperature of his scope. Keeping an f3 optical system in focus over a 14 degree temperature shift would be a spectacular design and engineering feat. If the design does allow this then kudos, other manufacturers like takahashi and AP have got a lot to learn.

[avandonk]

Originally Posted by cventer

"Focus was sustained, with no change, till the last frame came in at 04:02 in the morning. The temperature change during this 10 hour stretch was ~ 14 C degrees (from ~ +12 C down to ~ -2 C)."

I have to say I am somewhat skeptical of this claim. Bert another Rh200 user on this forum has gone to great lengths to control the temperature of his scope. Keeping an f3 optical system in focus over a 14 degree temperature shift would be a spectacular design and engineering feat. If the design does allow this then kudos, other manufacturers like takahashi and AP have got a lot to learn.

Cris I keep the whole image train at a constant temperature. I have found that the focuser and CFW are more prone to temperature changes than the RH200. It is impossible to keep the Atlas focuser and CFW at a constant temperature without also controlling the RH200 temperature. I am still in the process of tweaking this.

Just for interests sake on that really hot night when the whole optic train was at 29C rather than the set 20C. Focus had shifted by 1100 steps of the Atlas focuser. This is about 93 micron and nearly all of it was in the optic train behind the RH200. I have temperature sensors all over the place and when the RH200 was still at 28C due to the high tech towel and the Atlas focuser/CFW was close to 21C focus was almost back to what it was at 20C!

Bert

[cventer]

Thanks Bert

Thats why I am sceptical of the claim focus did not shift over a 14 degree temperature change. Just dont see how its possible.

[gregbradley]

Originally Posted by cventer

Thanks Bert

Thats why I am sceptical of the claim focus did not shift over a 14 degree temperature change. Just dont see how its possible.

It may be a different focuser setup. He may be using the standard Officina Stellare focuser which may be different.

I guess he would have to chime in and respond to that.

Looking at OS website it seems they have gone to a lot of trouble to ensure thermal stability-
http://www.optcorp.com/product.aspx?pid=16629

My experience with carbon fibre scopes is they can hold focus really really well. My CDK hardly changes with temp (so long as primary mirror and ambient are very close) and with a 12.5 inch RCOS focus was the same each night.

Greg.

[dvj (John)]

I can chime in here as I own one of these telescopes with the factory focuser. My unit holds focus across 3 degrees delta F quite well as measured FWHM betwen 10 minute subexposures. There is thermal setteling time however of about 45 minutes before you get started. This unit has no fans, no place for warm air to escape the tube.

jg

[gregbradley]

Originally Posted by cventer

Thanks Bert

Thats why I am sceptical of the claim focus did not shift over a 14 degree temperature change. Just dont see how its possible.

That's odd. The optcorp.com description of the scope says it has 3 fans at the primary. They deleted those or have added them recently?
http://www.optcorp.com/product.aspx?pid=16629

Greg.

[cventer]

Originally Posted by dvj

I can chime in here as I own one of these telescopes with the factory focuser. My unit holds focus across 3 degrees delta F quite well as measured FWHM betwen 10 minute subexposures. There is thermal setteling time however of about 45 minutes before you get started. This unit has no fans, no place for warm air to escape the tube.

jg

Thanks John

How about 14 degrees delta as the OP below described ?

[dvj (John)]

Originally Posted by cventer

Thanks John

How about 14 degrees delta as the OP below described ?

There are only a few of these scopes in actual use to get a lot of real user feedback. I'd be cautious of doubting performance this early. The unit is very well constructed and designed to be thermally stable at f/3.

[cventer]

Originally Posted by dvj

There are only a few of these scopes in actual use to get a lot of real user feedback. I'd be cautious of doubting performance this early. The unit is very well constructed and designed to be thermally stable at f/3.

I'm not doubting performance at all. Lots of good I images around. I'm doubting claims that any optical system with such short focal length could remain thermally stable over a delta 14 degree temperature drop.

At end of the day mirrors still cool down. Adaptors made of metal shift slightly. Ccd camera and filter wheels change slightly.

I'm hoping it is all true as I can see one of these in my shed at some point in the future.