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Manual filter wheel or slide

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#1 stubeeef

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Posted 09 June 2020 - 10:24 PM

Searched but it seems all the threads where more about AP, looking for a manual wheel or slide. Never used one, so taking recommendations.

 

Thinking about adding a filter wheel to big dob in work.

Thinking 5 position 2" and manual. 

Would like to have it heatable, and easy to use.

 

Oh and prefer value, so bang for the buck is my theme. 

 

Used with Feathertouch.


Edited by stubeeef, 09 June 2020 - 10:25 PM.


#2 jeffmac

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Posted 09 June 2020 - 10:36 PM

The wheel works well with refractors and sct's. Not so much with reflectors. The reason is that most reflectors don't have enough focus travel to bring all of your eyepieces to focus with the wheel in place. So the slide is your best bet.


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#3 sanbai

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Posted 09 June 2020 - 10:45 PM

I use the Baader UFC in my SCT and my refractor. With this scopes there is no problem. Not fully true , the refractor had too little in focus travel with my mirror diagonal and clicklock, but enough with the crappy native visual back or a prism diagonal.

As said before, for newtons you may lack in focus travel to add the filter wheel or slide. This is something I’ve to think seriously if I want to upgrade to a fast dob


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#4 stubeeef

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Posted 09 June 2020 - 11:32 PM

well its a fast dob, f3.4 so slide it is.

 

guessing heated is no big deal. so is one more reliable than another? I don't need expensive but I do demand easy/reliable.


Edited by stubeeef, 09 June 2020 - 11:34 PM.


#5 Allan Wade

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Posted 10 June 2020 - 01:03 AM

Hey Stu, take a look at the Moonlite filter slide. That’s what everyone I know with bigger dobs uses. It’s really nice quality, machined and anodised aluminium. Comes with a heated option which is a must where I am during winter.


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#6 Allan Wade

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Posted 10 June 2020 - 02:16 AM

1.jpg

 

2.jpg

 

It's not easy to find on the Moonlite page.

 

https://focuser.com/products.php

 

Edit: even that link didn't work correctly. Click on it and look for the slide under "CR 2 inch Format Newtonian Focusers".


Edited by Allan Wade, 10 June 2020 - 02:19 AM.

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#7 a__l

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Posted 10 June 2020 - 05:58 AM

You are introduced to misconception. Feathertouch does not fit into the MoonLite slider hole. Photo 1. There is a use case with SIPS. But there are drawbacks (to the twisting of coma corrector for collimation).
I modified the MoonLite slider for the Feathertouch using a milling machine. Photo 2.
MoonLite slider has a flaw. Plastic clamps for heating elements. They have fallen off over the years. I am now using a 12 V hair dryer

Attached Thumbnails

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Edited by a__l, 10 June 2020 - 06:02 AM.


#8 OldManSky

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Posted 10 June 2020 - 07:59 AM

If you have the back-focus, there are a couple of fairly inexpensive 2" filter wheels on Amazon...

 

https://www.amazon.c...91793851&sr=8-2


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#9 Jon Isaacs

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Posted 10 June 2020 - 08:12 AM

If you have the back-focus, there are a couple of fairly inexpensive 2" filter wheels on Amazon...

 

https://www.amazon.c...91793851&sr=8-2

 

I couldn't see where it said the amount of backfocus required.  Do you know?  Have you used one?

 

Jon



#10 kfiscus

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Posted 10 June 2020 - 08:56 AM

Astrocrumb has heated filter slides for dobs.

 

Plan ahead in your build to be sure that you don't have a spider vane in the way like many mass-produced dobs.


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#11 OldManSky

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Posted 10 June 2020 - 09:00 AM

I couldn't see where it said the amount of backfocus required.  Do you know?  Have you used one?

 

Jon

It's stated as 20mm.  I haven't used one, I have a ZWO motorized wheel smile.gif

 

The Astromania version on Amazon is the exact same wheel, just a little more expensive.  But its page has better specs and configuration pictures:

 

https://www.amazon.c...1_t1_B07FTBY8WN


Edited by OldManSky, 10 June 2020 - 09:02 AM.

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#12 Old Rookie

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Posted 10 June 2020 - 09:56 AM

Roger at Astrocrumb is willing to work with a customer to make sure the slide fits perfectly. 

 

Astrocrumb has heated filter slides for dobs.

 

Plan ahead in your build to be sure that you don't have a spider vane in the way like many mass-produced dobs.


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#13 Jon Isaacs

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Posted 10 June 2020 - 09:58 AM

It's stated as 20mm.  I haven't used one, I have a ZWO motorized wheel smile.gif

 

The Astromania version on Amazon is the exact same wheel, just a little more expensive.  But its page has better specs and configuration pictures:

 

https://www.amazon.c...1_t1_B07FTBY8WN

 

Thanks:

 

My 16 inch has a 4 inch secondary and the Focuser is setback to lower the eyepiece height so I think there is 20 mm for a filter wheel.

 

Jon


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#14 sanbai

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Posted 10 June 2020 - 12:26 PM

I don't have any experience with a Paracorr, therefore I have to ask:

 

Does its optical design leave space for a filter slide between the top lens and the eyepiece barrel (using the lower setting)?

This is not about the existing housing, only the optical design. Looking at the pictures it seems that there is enough space.

 

The paracorr has a filter thread, which allows to exchange eyepieces while using a filter without swaping it from EP to EP. However, I guess that adding a piece of glass in front of the Paracorr requires repositioning it. Please correct me if I'm wrong. If the filter stays between paracorr and eyepiece, it only requires tweaking of the tunable top, which should be easier given what I've read.

 

For me, the ideal would be that the Paracorr housing had a filter slide and a collet type mechanism (e.g. Clicklock) instead of a compression ring. I love the Baader clicklock and the Baader UFC (filter slide) - both used in a SCT and a refractor. Maybe TV should give just the basic optical cell to Baader so they can engineer something around it (dreaming...). Baader has a coma corrector but not really practical for 2" eyepieces.



#15 stubeeef

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Posted 10 June 2020 - 03:23 PM

Astrocrumb has heated filter slides for dobs.

 

Plan ahead in your build to be sure that you don't have a spider vane in the way like many mass-produced dobs.

I found them last night when I couldn't sleep, he looks great and I love supporting the little guy.

The slider would be for my 20" Starstructure f3.4, I reached out to steve a CN buddy with a 20" SST and he uses the orion 2" with his and has no problem.

 

I saw the moonlite system and when it was a match for their focusers, which I do like, I moved on. The astrocrumb is basically the same for the feathertouch. I love his boxes too, its the little stuff like that ya know.


Edited by stubeeef, 10 June 2020 - 03:29 PM.


#16 Jon Isaacs

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Posted 10 June 2020 - 06:47 PM

The paracorr has a filter thread, which allows to exchange eyepieces while using a filter without swaping it from EP to EP. However, I guess that adding a piece of glass in front of the Paracorr requires repositioning it. Please correct me if I'm wrong. If the filter stays between paracorr and eyepiece, it only requires tweaking of the tunable top, which should be easier given what I've read.

 

 

Adding a filter to the front of the Paracorr requires slight refocusing, outward, a fraction of a millimeter, about 1/3 the thickness of the filter glass.

 

With some eyepieces there's room between the eyepiece and the Paracorr for a filter.  With eyepieces like the 31 mm Nagler, the 21 mm Ethos, there's no room.  

 

There's no room in the Tuneable Top/ Paracorr for a filter slide wheel, it has to go in front.

 

Jon



#17 a__l

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Posted 10 June 2020 - 07:57 PM

Thanks:

 

My 16 inch has a 4 inch secondary and the Focuser is setback to lower the eyepiece height so I think there is 20 mm for a filter wheel.

 

Jon

Jon, Draw a ray path for P2+N31. I suspecting that you will have problems. Or this device or N31.



#18 a__l

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Posted 10 June 2020 - 08:03 PM

I don't have any experience with a Paracorr, therefore I have to ask:

 

Does its optical design leave space for a filter slide between the top lens and the eyepiece barrel (using the lower setting)?

This is not about the existing housing, only the optical design. Looking at the pictures it seems that there is enough space.

 

The paracorr has a filter thread, which allows to exchange eyepieces while using a filter without swaping it from EP to EP. However, I guess that adding a piece of glass in front of the Paracorr requires repositioning it. Please correct me if I'm wrong. If the filter stays between paracorr and eyepiece, it only requires tweaking of the tunable top, which should be easier given what I've read.

 

For me, the ideal would be that the Paracorr housing had a filter slide and a collet type mechanism (e.g. Clicklock) instead of a compression ring. I love the Baader clicklock and the Baader UFC (filter slide) - both used in a SCT and a refractor. Maybe TV should give just the basic optical cell to Baader so they can engineer something around it (dreaming...). Baader has a coma corrector but not really practical for 2" eyepieces.

When adding a filter, slightly adjust the focus (using the focus knob). It is highly desirable that the paracorr lens be as close to the filter as possible. Which probably does not fulfill the filter wheel. See my post above with the MoonLite slider.



#19 sanbai

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Posted 10 June 2020 - 08:04 PM

Adding a filter to the front of the Paracorr requires slight refocusing, outward, a fraction of a millimeter, about 1/3 the thickness of the filter glass.

With some eyepieces there's room between the eyepiece and the Paracorr for a filter. With eyepieces like the 31 mm Nagler, the 21 mm Ethos, there's no room.

There's no room in the Tuneable Top/ Paracorr for a filter slide wheel, it has to go in front.

Jon

Then, there is a case for a new product: a coma corrector with filter slide, self centering clicklock, and fine focusing + tuning mechanism. With a bayonet mount for easy attachment and detachment (like photo lenses).

Unfortunately,, the market isn't attractive enough. The mechanical part may be ok, but the new optical one is more difficult to deal with. Volunteers?

Edited by sanbai, 10 June 2020 - 08:06 PM.


#20 a__l

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Posted 10 June 2020 - 08:11 PM

I'm quite happy with the MoonLite slider on my telescopes. I have a Feathertouch focuser on 24" and MoonLite on 18". I do not see meaning.


Edited by a__l, 10 June 2020 - 08:12 PM.


#21 Jon Isaacs

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Posted 10 June 2020 - 08:19 PM

Jon, Draw a ray path for P2+N31. I suspecting that you will have problems. Or this device or N31.

 

I think it would work.The 31 mm vignettes slightly with the Paracorr 2 but the way the scope is setup it has a baffle in front of the Focuser already.

 

Assuming the filter slide has full aperture.

 

But realistically, it probably won't happen.

 

Jon



#22 a__l

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Posted 10 June 2020 - 08:28 PM

MoonLite slider has an extra large hole for use without filters. So no problem for the N31.



#23 mkothe

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Posted 10 June 2020 - 11:26 PM

I found them last night when I couldn't sleep, he looks great and I love supporting the little guy.
The slider would be for my 20" Starstructure f3.4, I reached out to steve a CN buddy with a 20" SST and he uses the orion 2" with his and has no problem.

I saw the moonlite system and when it was a match for their focusers, which I do like, I moved on. The astrocrumb is basically the same for the feathertouch. I love his boxes too, its the little stuff like that ya know.


I’m very happy with my Astrocrumb slide. I had the Moonlite which was also nice, but I was interested in shaving a bit of weight off and have an extra hole, so I decided to order from Roger. It was a pleasant surprise that he lives 10 minutes away from me, so I could stop by and pick it up in person! Roger is a great guy and very accommodating.

Best,
Michael
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#24 a__l

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Posted 10 June 2020 - 11:33 PM

Yes, I bought such a slider. Back in the days when I used SIPS. With fastening on the thread of the coma corrector. Plywood base. It turned out to be very inconvenient for working with SIPS. Large gaps (~3 mm!) when driving and generally plywood ... now I have it without movement...

 

As for the weight, I replaced the plywood rings on my 18" with carbon. I used a thin carbon baffle. A titanium bolt for the secondary holder and others. This greatly facilitated the weight of the telecope. That was enough even to use an aluminum slider. For a 24" telescope, this weight does no influence.

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Edited by a__l, 10 June 2020 - 11:51 PM.


#25 Jsquared

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Posted 10 June 2020 - 11:41 PM

I’m thinking about eventually getting a f4 16” dob with SIPS. Anyone fitted a filter slide to a SIPS equipped scope ?


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