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Returning to Long FL Imaging.

ollypenrice

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ollypenrice

ollypenrice

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Since Yves moved from our joint project with his 14 inch over to our robotic shed, and the Mesu began its new life carrying the double Tak widefield imaging rig, we've had nothing longer than a metre FL for imaging here. (The TEC140 works out at about a metre with flattener.) When our regular guest Frans Kroon said, this week, that he was selling his Meade ACF 10 inch my evil brain began to do what it's good at - plan on spending money!

2.5 metres of focal length gets us back into the galaxies and little planetaries. The scope's indistiguishable from new, I know it works and is collimatable (unlike one which was driving us nuts last week), it's fully loaded with Moonlite focuser, dew heater, optional Astro Physics reducer, dewshield, two dovetails, B-mask... it was making a case for itself. It was also here, so no need to pay any couriers to stick a fork lift through it. And no diff spikes. And no need to pull it apart regularly to clear out the autumn leaves...

A few emails later another of our robotic mount owners, Peter, said he'd make his mount available for it so... the deed was done. Frans suggested a price and I said Yes.

For robotic use it will have to work at F10 because we can only automate focus on the Moonlite, not the moving mirror, and it's 'either/or' between the AP reducer and the Moonlite. You can't use both together. Will the robotic 10 Micron do 2.5 metres unguided? Watch this space. We don't know. Since the targets will be small the F ratio really doesn't matter, aperture being the thing. However, with the reducer it could make a non-robotic imaging partner for the TEC on qutie a few targets.

If we use Peter's QSI683 binned 2x2 we get 0.89 arcsecs per pixel. If we use one of our Atik 11 megs we get 0.74 unbinned. (The 14 inch used to give us 0.66.)

What-ho, it's worth a punt and it would be nice to be able to give folks the chance to play with some long FL data as well as widefield. Here we are. The Losmandy is Frans' mount. (As is the scope since I haven't paid for it yet. The Penrice Kid moseyed into town, hitched his horse to the rail outside the bank, un-holstered his Colt and made his usual monthly withdrawal of 50,000 dollars...)

Meade%2010%20inch%20ARC-L.jpg

Olly

PS Yes, I know what kind of focuser the Moonlite is. No need to take the Mick, I know, I know...:icon_albino:

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swag72

swag72

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I look forward to seeing your results with the long focal lengths - You always did a cracking job with the ODK14. I would think that the 11000 would be a perfect match and that's what I'd stick on it.

It's interesting - I always smile when I put the long focal length scope on as I love it ....... then I smile when I revert back to the Tak..... I'm sure you'll enjoy it :)

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michael.h.f.wilkinson

michael.h.f.wilkinson

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I am not so much surprised at the C--------- focuser turnaround, but combining it with an SCT at native F/10 for DSO work? Do two wrongs combine to make a right?? My, my, strange times indeed ;)

Seriously, that looks like a very nice instrument to me, but then I am an SCT guy (still with the same old grotty focuser too)

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ollypenrice

ollypenrice

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Just now, michael.h.f.wilkinson said:

I am not so much surprised at the C--------- focuser turnaround, but combining it with an SCT at native F/10 for DSO work? Do two wrongs combine to make a right?? My, my, strange times indeed ;)

Seriously, that looks like a very nice instrument to me, but then I am an SCT guy (still with the same old grotty focuser too)

All down to the F ratio myth, Michael. I'd like to be able to offer a 2.5 metre FL. Ideally  that would be at F5 and so an aperture of 500mm. Well, that ain't going to be happening! So we will just have to plug away with the aperture we can afford and afford to mount. If time doesn't allow sufficient data for a full size rendition we can resample downwards and get much the same result as we'd get with a faster 10 inch scope. But at least the slow one gives the option of a long slog. In a nutshell a shorter, faster scope isn't what I'm after and a faster scope of the same length isn't what I can afford!

Do you reckon I could convert that Crayford into an R and P by cutting ridges into it with a junior hacksaw? :blob3:

Olly

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michael.h.f.wilkinson

michael.h.f.wilkinson

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1 minute ago, ollypenrice said:

All down to the F ratio myth, Michael. I'd like to be able to offer a 2.5 metre FL. Ideally  that would be at F5 and so an aperture of 500mm. Well, that ain't going to be happening! So we will just have to plug away with the aperture we can afford and afford to mount. If time doesn't allow sufficient data for a full size rendition we can resample downwards and get much the same result as we'd get with a faster 10 inch scope. But at least the slow one gives the option of a long slog. In a nutshell a shorter, faster scope isn't what I'm after and a faster scope of the same length isn't what I can afford!

Do you reckon I could convert that Crayford into an R and P by cutting ridges into it with a junior hacksaw? :blob3:

Olly

The conversion might invalidate the warranty on the focuser :D

 

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ollypenrice

ollypenrice

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1 hour ago, ncjunk said:

Sorry what's going on? I was looking out the window daydreaming of large telescopes. I hope there's not a test on this.

Should be a fun setup to test.

I'm thinking of M66 which is tantalizingly gorgeous even at short FL. It will frame with M65. Indeed it would only be two panels to do a high resolution Triplet but the tidal tail at F10 might take a while...

Olly

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ollypenrice

ollypenrice

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9 minutes ago, swag72 said:

Have you decided what camera to use with it Olly?

Not yet, S. Since Tom has megalomaniac schemes for another big summer mosaic he'd like to have all the full frames avaiable so maybe we'll start with Peter's QSI binned 2X2.

That would mean one at once for the Triplet.

Olly

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ollypenrice

ollypenrice

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3 hours ago, theastrodragon said:

Are you going to be trying for unguided on the Losmandy? Because while mine was nice, it wasn't up to that.

They guide out the PEC well, but no way are they up to the 1" or so PEC I suspect you would be needing.

 

No, the Losmandy isn't mine, it's here with the guest who's selling the scope. Unguided would be on a 10 Micron. We coud always guide if necessary, though.

Olly

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perfrej

perfrej

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This will be fun! I need to upgrade your firmware. The latest FW has some improvements to GM1000HPS unguided tracking. My first test sub was a half-hour one and Maxim reported roundness of 0.02. Let me know when I shall do it for you. Jonas and I have already done our mounts.

 

/p

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ollypenrice

ollypenrice

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5 hours ago, Skyline said:

http://www.stanmooreastro.com/f_ratio_myth.htm

I know. I'm a great believer in all of this. That's why I'm prepared to buy an F10 scope for imaging small faint targets.

Olly

5 hours ago, perfrej said:

This will be fun! I need to upgrade your firmware. The latest FW has some improvements to GM1000HPS unguided tracking. My first test sub was a half-hour one and Maxim reported roundness of 0.02. Let me know when I shall do it for you. Jonas and I have already done our mounts.

 

/p

Thanks Per. I'll give Peter a heads up. He's boating at the moment but I'll see him in just over a week.

Olly

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  • 3 weeks later...
ian_bird

ian_bird

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Olly

You mentioned the "optional Astro Physics reducer".

I have one - which I am just about to add to my GSO 250mm RCT.

I have the spacing from the reducer to the CCD sorted out (in my head) but I have one big doubt.

Does adding the reducer change the focus point?

Say for example I can get good focus with the drawtube extended 19mm out when I don't use the reducer.

If I add the reducer *without* changing anything else - including the length of the image train (the reducer will sit inside the drawtube and add no physical length to the setup) - will my focus position change?

And is there anyway to calculate by how much?

I stress - I am not talking about the reducer to CCD distance - just the affect it will have on where I find focus. 

Any insight greatfully received.

Cheers

Ian

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ian_bird

ian_bird

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Olly

Found it! Below is a quote.

It's not a linear relationship. The distance that the focus point moves inwards is:

a - ( b x a ) / ( b - a )

where a = distance of CCD from FR and b = focal length of FR.

Sorted.

Cheers.

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Tyson M

Tyson M

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Gorgeous scope!!! Congrats

 

Funny, A deal came up through a friend of mine also here in Canada for the exact scope! 10" ACF F10. 

 

Comes with a Meade focal reducer/flattener, upgraded focuser (Williams Optics DDG), Bob's knobs, losmandy rail, and I know he takes great care of his gear because I bought a preowned AZEQ6 of him last year.

 

I was looking for something special for planetary imaging and general viewing. Was going for a Mak 180 brand new (for the viewing not so much for the imaging), he suggested an SCT and said he had too many he would make me a good packaged deal.

 

I couldnt say no and loved the views through a friend's C11 Edge, which is similar. I've never had an SCT and was apprehensive acquiring a pre-owned one, but not in this case. 

 

I am really excited. I still need a dew shield and heater and a case. But I will figure it out. 

 

I am looking forward to your images! 

 

 

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Scott

Scott

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On 4/4/2016 at 14:48, ollypenrice said:

All down to the F ratio myth, Michael. I'd like to be able to offer a 2.5 metre FL. Ideally  that would be at F5 and so an aperture of 500mm. Well, that ain't going to be happening! So we will just have to plug away with the aperture we can afford and afford to mount. If time doesn't allow sufficient data for a full size rendition we can resample downwards and get much the same result as we'd get with a faster 10 inch scope. But at least the slow one gives the option of a long slog. In a nutshell a shorter, faster scope isn't what I'm after and a faster scope of the same length isn't what I can afford!

Do you reckon I could convert that Crayford into an R and P by cutting ridges into it with a junior hacksaw? :blob3:

Olly

Perhaps a series of rubber bands rapped around the tube?

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