Thin Filter Wheel with 7x1.25"

[badgers]

Hi All,

I've got an Atik MFW 5x1.25" manual filter-wheel (http://www.atik-cameras.com/products/info/atik-mfw)

It's really thin (19.5mm) which is just as well because my refractor flattener needs 51.5mm and I just about make the distance with an OAG.

My problem is that I'd like to upgrade to a 7x1.25" manual or electronic filter wheel, but I need one that's not going to add length to my imaging setup.

Ideally it would be less than 20mm thick with female t-threads either side.

I've got narrowband filters coming, and I don't like the idea of opening up the filter-wheel to access the carousel every time I want to go narrowband.

Any ideas ? Most of the ones I see online are at least 21mm thick.

The only other thing I can think of is to see if I can find a 7x1.25" carousel that would fit and try and bodge something.

Thanks,

Anton

Quantum filter wheel: 21mm

Atik EFW2: 22mm

True Technology filter wheel: 21.5

QHY filter wheel: 18.5... perfect but it only takes 2" filters

SXV filter wheel, hard to tell the width online, looks at least 20mm but has some complicated adapter arrangement.

[steppenwolf]

Just for the record, the SXV filter wheel would also not resolve your issue

[Earl]

Anton which OAG are you using? I personally think it will be easier to get slimmer OAG over a Slimmer filterwheel.

I just noticed your sig (bit hard to read in purple though )

is this the one?

http://www.teleskop-express.de/shop/product_info.php/info/p377_TS-Off-Axis-Guider---nur-27mm-Baulaenge---fuer-Astrofotografie.html

[badgers]

Hi Earl,

Sorry no, it's the super slim OAG from TS:

http://www.teleskop-express.de/shop/product_info.php/language/en/info/p641_Off-Axis-Guider---nur-9mm-Baulaenge---T2-Anschluss---fuer-CCD.html

Any slimmer than that and I'd need pixies to hold the prism in place

To be fair the problem is the flattener, 51.5mm is a punishingly short distance to work with,

but the results from it are great and I quite like having a short imaging train.

Anton

[badgers]

Thanks for the confirmation on the SXV wheel Steve.

[Earl]

humm it should be doable with the super slim.

Can you share your numbers, connectors the whole kaboodle.

And some photos too

[badgers]

Hi Earl,

This is the imaging beast on the flattener...

Flattener M48 -> TS 9m OAG (M48:T) -> Atik MFW -> Astroboot slim T-coupler -> Atik 460.

Spacing is 53mm currently and its just about flattening perfectly.

I guess I'd need to find 1 or 1.5mm somewhere to allow me one of the 21mm filter wheels.

I'm not sure where I can save more space though, that's why I was praying for a slim 7 slot wheel : (

Anton

[Earl]

The atik camera attached to the efw2 has zero length as its a flush fit iirc, that should save you that 1-2mm

humm rereading it saves you .5mm as its thicker.

getting the OAG in as tight as possible is the next task.

The end of the Flattner is M48 this screws straight into the OAG, but it looks like there is quiet a gap there, is this due to the thread been too long on the reducer ?

[badgers]

Earl, you are a star... I reckon I'm loosing at least 2mm due to having the adapter between filter wheel and camera....

That EFW2 would likely do exactly what I need. I had no idea it threads right onto the camera without an adapter....... brilliant

And yes the reducer thread is too long so there's quite a bit stuck out of the M48 side of the OAG.

[Earl]

Looking ahead you will need to adapt from the output of the EFW2 to the OAG, Bern does a very nice M54 to T Male which only adds 1mm. the one of the QHY filter wheel

[badgers]

Ouch... I just saw the price.... guess I'll be saving up for that then

[Earl]

Is there a way to remove the glass from the reducer and get a few mm ground off the thread as that will help you out too.

[Earl]

My little Rant.

Whoever designed filterwheels really needs to look at connectivity and excessive thickness.

Job one is like the Atik EFW2 but have a rotatable but zero lenght ports with options for size of port Maybe M72, M62, M54, M48 and T thread

These need to fit from the inside not externally. the outsides need to be flush with what ever you are connecting.

All the Filterwheels I have had have too much space on either side of the wheel id guess a 2-3mm thinner is more than doable even with thick walls as the walls can allow the edge case to sit in them.

Both sides should be removable not just one.

give me a wheel and ill redesign that too HAHAH

[badgers]

I've got to say I agree..... or use the extra space for something useful like an OAG port.

The EFW2 will definitely solve my problem, and Teleskop Service can even adapt it so the TS OAG fits it completely flush.

But at £500 I'm not sure its a good investment for me at the moment just for the convenience of 2 extra filter holders.

For that money I could buy a 2nd hand carbon fibre imaging newt or a riccardi reducer for my refractor...

For now I'll probably just take the filter wheel apart for narrowband nights.

Only other option is to buy one of the cheap 7x1.25" wheels and saw off excess thread from my t-adapter to come in another mm or two with the camera and hope it makes up the difference.

Anton

[Spikey]

Quite happy to measure the distances from my reducer to chip on my SX filterwheel which is 7x1.25.

Same reasons for purchase as yourself Anton, I wanted to upgrade from a manual 5x1.25 and also drop the NB filters in at the same time without having to dismantle.

[badgers]

Thanks Simon, that would be useful. The key measurements for me are the distance across the wheel and distance coming from wasted thread on the CCD side.

I also had a chat with Bern at Modern Astronomy, he suggested two things.

a) To go for a quantum 7x1.25" wheel and use a continuous male male t-thread ring short enough to bring the edge of the CCD flush to the filter wheel.

The filter wheel would be 1.5mm wider than my current one, but I'd likely save 2mm by going flush to the wheel. I don't see any very short male-male t-thread's so I'd probably have to take a few mm off it.

To use a shrinking ray.

I think he was joking about option b.

[ollypenrice]

Maybe not what you want to hear but an OAG is not at all essential on a small refractor. That's just if push comes to shove, at least.

Olly

[badgers]

True enough Olly.

I never had a great guidescope setup though, I always had just too much flexure in the rings, it probably would have been ok with the refractor though.

If I went back to guidescope, I'd want to do it properly and get good quality rings and a better guidescope which might cost some money.

Anton

[badgers]

Problem solved!

I took a punt on the Brightstar 7x1.25" electronic wheel after chatting with Bern at Modern Astronomy. It arrived today and I really like it.

My OAG adapter screws directly into it, so I'm saving 1mm over the Atik already.

I took the male-male T adapter that came with it and sawed off the end that goes into the wheel right to the flange.

I filed back everything flat and repainted it with blackboard paint.

Then I screwed this back through the filter wheel so the flange is internal and outside (CCD side) I only have about 5mm of pure T-thread, so the Atik can screw right to the wheel.

I had to adjust the internal spindle and the little sensor slightly higher with some delrin washers, but everything is now working perfectly and I've gained back at least 5mm.

So I've now got all 7 filters and I'm hopefully bang on target for Sensor Flattener distance.

Thanks for all the advice and feedback,

Anton

[Earl]

Good new Anton, im awaiting an adapter from Bern to hook up my new Focuser to my Filterwheel.