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Manual filter wheel or slide

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#26 a__l

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Posted 10 June 2020 - 11:58 PM

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

Yes, that is what SDM does. There is a problem, when collimating, you need to unscrew the coma corrector. Try to unscrew it through the slider. In addition, SIPS has other problems, but this is not this thread.



#27 mkothe

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Posted 10 June 2020 - 11:59 PM

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.


I should clarify that the weight difference is not that great and my ballscope is particularly sensitive to balance, so this will not be an important consideration for many. I am happy with the mechanics of my slide (used without SIPS on a feathertouch). But the Moonlite was also very nice. I prefer the warmer feel of the (balsa?)wood, but again, a minor difference.

Michael

#28 Bill Weir

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Posted 12 June 2020 - 01:24 AM

Every once in awhile I think of getting a filter slide (Astrocrumb) but don’t they add a whole bunch extra into the light path? Someone I know and respect as a deep sky observer swears by his. 

 

Bill



#29 a__l

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Posted 12 June 2020 - 05:41 AM

Every once in awhile I think of getting a filter slide (Astrocrumb) but don’t they add a whole bunch extra into the light path? Someone I know and respect as a deep sky observer swears by his. 

 

Bill

My Astrocrumb cuts the light cone, especially for my fast dob. My other (MoonLite - post # 7) is not. Therefore, I use MoonLite. They are both mine. The first one is unfortunately.

 

Ps. I consider a situation without a filter. With a filter cuts a 2" filter (for MoonLite slider - install your focuser correctly to minimize the effect). And another refinement. I always use paracorr-2

And another significant nuance. MoonLite slider allows me to use Denk bino (the filter is installed on OCS if necessary).

Attached Thumbnails

  • Astrocrumb (1).jpg

Edited by a__l, 12 June 2020 - 06:50 AM.


#30 Bill Weir

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Posted 12 June 2020 - 10:53 AM

Ok, one cuts the light cone with my fast scope and the other might need milling to make it work correctly, that’s a decision maker for me. It’s not all that hard to pull the Paracorr and change the filter.

 

Bill


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#31 stubeeef

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Posted 12 June 2020 - 11:39 AM

Anyone here using the Orion 2" 6 filter slide?

 

https://www.amazon.c...r/dp/B00XREJSJ0

 

I know it says not recommended for newts but a buddy uses on this 20" starstructure and loves it


Edited by stubeeef, 12 June 2020 - 11:43 AM.


#32 Old Rookie

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Posted 12 June 2020 - 04:30 PM

Every once in awhile I think of getting a filter slide (Astrocrumb) but don’t they add a whole bunch extra into the light path? Someone I know and respect as a deep sky observer swears by his. 

 

Bill

Mine does not intrude into the light path - it isn't even close.  I discussed  my requirements with Roger and he built the slide to work on my dob.  It has two spots for filters: one at the top and one at the bottom.  The center spot is open.  The slide is heated also.  I've got to say that Roger sent it to me and it was a bolt on, flawless install.  

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  • FilterSlide.jpg

Edited by Old Rookie, 12 June 2020 - 04:32 PM.


#33 mkothe

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Posted 12 June 2020 - 04:58 PM

Ok, one cuts the light cone with my fast scope and the other might need milling to make it work correctly, that’s a decision maker for me. It’s not all that hard to pull the Paracorr and change the filter.

Bill


Mine protrudes a bit into the path of my 12.5”, but I don’t notice any effect on the images. I find the convenience of sliding the filters is huge compared to screwing and unscrewing filters. So easy to see which one works best. I would use filters much less without the slide. In fact My filters came with the scope and I never used them before I got the slide.
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#34 a__l

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Posted 13 June 2020 - 01:15 AM

In the photo is my MoonLite slider. Pay attention to this gap (red arrow) in Astrocrumb. On wood, it is difficult to maintain the exact dimensions. This gap can shift some of my filters up to 3 mm and more in my Astrocrumb. This is another reason for cut the light cone. On MoonLite this is not.

 

NV requires 1 minimum filter (H-Alfa). For comparison with a regular eyepiece, another 1-2 filters are needed (OIII and UHC). Need to switch quickly. Some objects appear differently in OIII and H-alfa and this is interesting.

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  • Slider_18_.jpg

Edited by a__l, 13 June 2020 - 02:28 AM.


#35 Jon Isaacs

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Posted 13 June 2020 - 05:15 AM

Mine does not intrude into the light path - it isn't even close.  I discussed  my requirements with Roger and he built the slide to work on my dob.  It has two spots for filters: one at the top and one at the bottom.  The center spot is open.  The slide is heated also.  I've got to say that Roger sent it to me and it was a bolt on, flawless install.  

 

What all supports the Focuser? That upper ring looks thin to me.

 

Jon



#36 Old Rookie

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Posted 13 June 2020 - 08:15 AM

What all supports the Focuser? That upper ring looks thin to me.

 

Jon

Three struts and six strings.  The focuser bracket is 1/4" aluminum.  The upper ring is 1/2" plywood.  The six strings keep everything tight and relatively "solid."



#37 kfiscus

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Posted 13 June 2020 - 11:45 AM

For those considering an Astrocrumb filter slide, please know that there are 2 different styles.  I use the original style that bolts directly to the body tube.  There is very little to any light blockage since the rails are tucked up tight against the tube.  The Astrocrumb Mk II model clamps onto the draw tube and blocks some light.



#38 Jon Isaacs

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Posted 14 June 2020 - 05:40 AM

Three struts and six strings.  The focuser bracket is 1/4" aluminum.  The upper ring is 1/2" plywood.  The six strings keep everything tight and relatively "solid."

 

I'm concerned about the ring tilting out of plane with a heavy eyepiece and possiby a Paracorr.  That's a fair amount of bending moment.

 

My 16 inch has a 3/4" plywood upper ring and I added a 5/16" piece to stiffen that span. The bending stiffness is proportional to bh3 where b is the width and h is the thickness, a 1 inch thick ring is 8 times stiffer than a 1/2 ring.

 

Jon



#39 Old Rookie

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Posted 14 June 2020 - 02:25 PM

I'm concerned about the ring tilting out of plane with a heavy eyepiece and possiby a Paracorr.  That's a fair amount of bending moment.

 

My 16 inch has a 3/4" plywood upper ring and I added a 5/16" piece to stiffen that span. The bending stiffness is proportional to bh3 where b is the width and h is the thickness, a 1 inch thick ring is 8 times stiffer than a 1/2 ring.

 

Jon

Visually, it hasn't revealed itself to be a problem.  



#40 a__l

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Posted 14 June 2020 - 07:16 PM

This is easy to verify. Install the laser collimator. Press on it with a finger with a weight approximately equal to the weight of your heaviest eyepiece (plus paracorr, if used). Watch the beam.

My second edition 18" was with one plywood ring (20 mm thick). I refused it because of its weakness and made the 3rd edition of 2 carbon rings (photo above). Now I am satisfied :)


Edited by a__l, 14 June 2020 - 07:21 PM.



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