Quick first light OMC140C

[argonaut]

Last night was the first opportunity to have a look through the new scope.

The seeing was terrible ,but I just wanted to look through it!

I had a SCT-2" adaptor,2" diagonal and 28mm UWAN. This gave me 71x and just over 1° FOV. I was concerned about the length of the light path,but the concerns were unfounded. It did reach focus.

I did leave the scope an hour to cool down. The view of Polaris was terrible,it wouldn't even split at 71x due to the seeing. Some high cloud did improve the view somewhat. I've seen this happen before with my refractors. Nowhere near 'pinpoints of light I'm afraid.

From what I could see there were no collimation problems with the scope. I am going to have to wait and reserve judgement for now. I just wanted to make sure everything 'worked'. The microfocuser seemed OK (not that I could really focus on anything) I couldn't feel any play in it and it seemed pretty good at doing it's job.

The 8x50 finder scope was OK and did it's job.

Apologies for the pretty boring first light.

Glen.

[philsail1]

Glen,

I think everyone will understand your excitement (and frustration) at wanting to get out with your OMC140!

Regards,

philsail1

[Pauls]

Glen

Orion Optics sell cooling fans a push fit one

Paul

[lunator]

Glenn

Glad you got out last night

The scope will show great views whenthe sky co-operate.

Cheers

Ian

[argonaut]

I had second light last night. I had a three hour cloudless window. It's been a while since one of those.

I put the scope outside at 8pm to cool for an hour. Checking Polaris and the airy disc(which was circular) when I put it out. I could certainly see tube currants.

At 9pm I checked again. This time the airy disc was oval? Now that's some cooling. The image was no better although I still couldn't split Polaris at 71x.The tube currants were still there.

At 10 pm things were looking much better. The airy disc was round again and no tube currants. I could easily split Polaris.

At 10.30 it was pretty good with round airy disc and again no currants. I pushed the mag up to 125x and finally 286x,at 286x the image was terrible.

While at 71x I had a look at some of my favourites.

M45

NGC457

Double Cluster

Mizar/Alcor

The images are not as crisp as my TV85.I still don't have pinpoints of light. I just wondered if this is a trait of Maks?

I must say through stupidity on my part that I bought this as a grab&go scope. I think I'll stick to refractors and binoculars.

Thanks for your comments lads.

Glen.

[John]

Hi Glen,

Thanks for posting the report

I reckon the OMC140 should produce refractor-type images on a night of good seeing, when the optics are fully cooled and assuming that the scope is well collimated.

The Tele Vue 85 is a tough act to follow though - it's considered a kind of optical benchmark against which other scopes are measured by many.

Don't despair - things will all fall into place soon I'm sure. You can get cooling fans to help maks and SCT's cool as Paul says.

John

[argonaut]

Hi John,

Got to agree with the refractor images. The stars do seem bloated in the Mak. The image was brighter though, due to the aperture no doubt. I am going to stick with it. It's just me feeling a little disappointed.

It was good to get out last night at least.

I have been looking at a Lymax cooler for it. I just don't want the carbon dust flying around again. I think the inside of the tube needs flocking or at least sealing with something.

Glen.

[Brass n glass]

I've had an OMC140 with quarter wave mirror and Hilux coatings for five years. Cooling time is often nearer 90 minutes than an hour and in image sharpness it falls just behind my TV76, but not far behind. It's the only Mak I've ever had, and it reacts to seeing conditions much more than any refractor i've ever used. It sulks in moderate to poor seeing, but in really good conditions it will sometimes stand powers of up to 400X on a few objects such as Saturn. It splits Polaris with no trouble at all, but cooling time is absolutely critical - Hugh.

[argonaut]

Hi Hugh,

Thanks for that. It's just that I have to get my 'refractor head' around Mak problems.

I'm not sorry I bought the scope.I am certainly learning more about optics that is for sure. No doubt there will be better nights ahead. It's my expectations that were a little off.

I have found it difficult to find out the cause of bloated stars. I have posted this on a couple of forums but I've not really had a answer to this question yet.

Glen.

[Brass n glass]

Maybe try leaving it out for two hours before using it; then you'll be certain you won't have any cooling issues. If you still get bloated stars, perhaps it will be either collimation or, more likely, atmospheric turbulence. These frosty nights can be like looking into a goldfish bowl when the fish is swimming around. Refractors can cope with that, no problem, but my OMC140 doesn't like it - Hugh

[argonaut]

I'm going to leave it alone for a while and wait until someone else gets their carbon tube version. There should be some around by now I would have thought?

I have collimated Dobs in the past. I've never had these sort of problems before. It's the all important cool-down time and seeing. Must be a Mak characteristic. There is one positive out of this. I have been doing alot of reading on Mak optics that's for sure.

Thanks for the input Hugh.

Glen.

[argonaut]

Just an update.

I was out last night with the OMC during a window in the snow. I have now bought a fan from OrionOptics. The fan didn't seem to make much difference last night. The images were soft again and a little bloated. The seeing couldn't have been too bad because I had a 10" Dob set up next to it and the images were fine.

I e-mailed OO again to see if someone could pinpoint the problem. Quick answer from John. I could take it back to check collimation. Now,tonight I thought I would have another go. Stuck the fan in to start up for 15 minutes.What a difference,the seeing must have been better. The Moon was breathtaking at 250x. Venus would only take 63x though. The stars were less bloated. I think it's a little bit of bad seeing and collimation a little off. Anyway,that's the story so far.

Any ideas on a filter material for the fan unit ? Here's a pic of the unit.

Glen.

[GazOC]

Any ideas on a filter material for the fan unit ? Here's a pic of the unit.

I might well be wrong but I think those fans suck warm air out of the scope, not cold air in.

[Dangerous-Dave]

Interesting stuff! I've just bought an OMC140, a second hand non-hilux version, and while I only got the chance to point it at the moon and Venus, I thought it delivered very sharp results. I don't own a TV85 (would like to afford one) but I do own the WO Megrez 90 and in my opinion the OMC does a more than adequate impression of a fluorite doublet.

I keep the scope in a cold conservatory (about 6-7 degrees ambient temperature) but I too noticed tube currents for quite some time after setting up. It certainly needs more cool down time than I gave it (err....about five minutes! :oops: ) so the fan looks very interesting (pity about the crocodile clip power leads though).

My main interest is in imaging and I found it a capable performer despite the tube currents. There are some shots on my Flickr page. It really needs a proper cool down though, and I need to check the collimation next time the stars are out.

[argonaut]

Gaz, never thought to check the rotation I have just checked and it seems to suck out more than blow in. It's strange in that I can feel a flow both ways :?

The scope did seem better tonight.

Glen.

[argonaut]

Dave,

congratulations on the scope.

I just thought I would keep updating as I go along with the OMC. I'm very new to Mak's and was a little disappointed. I'm getting there though. Been doing a lot of reading on Mak optics lately.

You're right about the cool down time though.Something I may have to get used to at this time of year. I was pleased with the Moon and Venus tonight. The fan certainly seemed to work tonight. I could always put 'Tamiya' plugs on it pretty easy.

Some nice pics you've done Dave :salute:

Glen.

[argonaut]

Any ideas on a filter material for the fan unit ? Here's a pic of the unit.

I might well be wrong but I think those fans suck warm air out of the scope, not cold air in.

Hi Gaz,

No,they take cold air into the OTA. There is a 'air gap' between the corrector and the corrector holder. Any idea's on filter material anyone?

Glen.

[GazOC]

I stand corrected Glen, I'm sure I've read somewhere that scope fans for Maks and SCTS pull air out. I guess my memory is playing tricks......

[argonaut]

I ran it earlier and it does draw cold air in. Never thought to check before you mentioned it. I'll probably try a linen snotty and see if that keeps the dust out.

Maybe,Orion do it different

Clear Skies.

Glen.