11 replies to this topic

[rexowner]

I'm looking at adding a filter slide to a custom Dob, with which I intend to use the TNVC/Tele Vue

afocal system, probably a slide from Astrocrumb:

https://astrocrumb.com/

They will make the slide to handle different numbers of filters.  My thinking is that 4 places

would be enough for NV with wide/narrow Ha and maybe a couple of long pass filters,

but they e.g. could make a 6 or 8 place slide.  I don't want to over-do it, but what

would you say would be a good number of filter places?

[jay.i]

You probably don't need more than 4 filters. For the SF Bay Area, I'd say Baader 685nm for galaxies and clusters around home, Astronomik 642nm for better MW and some nebula visibility under slightly better skies, Astronomik 6nm/Baader 7nm H-a for nebulae under everything except maybe the darkest skies, and an Antlia 3.5nm H-a for very high contrast nebulae with afocal. You could swap the 3.5nm H-a for a 12nm H-a for dark sky visits.

 

Yeah, 4 should be fine. I'd recommend 2" filters so you can do afocal use to get some real speed to make nebulae pop (esp with a really narrow H-a filter). 

 

It looks like the Astrocrumb system has an open hole for unfiltered viewing, which makes sense. In that case, a 6 hole filter would be the way to go, so you can store 5 filters.

[Solar storm]

I have an Astrocrumb on my 11" dob for NV and it is great.  Definitely a awesome upgrade.  

[nimitz69]

Unless you plan to use the scope under a lot of different sky conditions you don’t need very many filters.

I observe from basically the same skies all the time (SQM 19.5) and I just have one 7nm Ha & 1 642 LP filter.

I would think 4 positions would be plenty

BTW, this will be teh perfect solution for my 14” Dob if the 5-position filter wheel I just got can’t come to focus. I’m definitely tired of changing expensive filters in the darks!

Edited by nimitz69, 14 September 2020 - 06:05 PM.

[GeezerGazer]

I might suggest at least one slot that can be left open, for viewing without a filter in the light path.  I agree with Nimitz, in that only 3 filters are plenty, probably using just one long pass filter appropriate for your typical sky conditions, your choice of two H-a; I'd choose 12 and 3.5 for my skies with my scopes.  Good luck

[a__l]

I do not recommend buying this slider. I have one, I believe that this is wasted money. He rest without any movement.
If you have a MoonLite focuser, don't hesitate to buy their slider. If Starlights, there are some compatibility issues here. I modified the Moonlite slider on my milling machine.

Edited by a__l, 14 September 2020 - 09:58 PM.

[ButterFly]

The astrocrumb slide works just fine on a feather touch (Starlight).  No compatability issues at all.  Bear in mind that they come with one hole with no threads as standard.  When building, leave enough room (about an inch) so that it doesn't interfere with the light path, unless it's too late.

 

NV filters are quite different from visual filters.  Another slide for the NV stuff is probably a better idea.  Parfocal filters don't matter at higher eyepiece focal lengths, but they come in very handy at lower eyepiece focal lengths.

[a__l]

The astrocrumb slide works just fine on a feather touch (Starlight).  

They suggested that I buy this slider with SIPS. That was my mistake.
You might wonder why SDM doesn't install these sliders with Starlight.

[The Ardent]

I don’t think it’s available anymore, but I like the Earthwin system since I had all 2” filters . It’s a coma corrector, power switch , 2 filter slide, and 2” eyepiece holder in one unit. 

https://www.cloudyni...f/#entry7722219
 

 

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[ButterFly]

They suggested that I buy this slider with SIPS. That was my mistake.
You might wonder why SDM doesn't install these sliders with Starlight.

Who are they?  It's only one person at astrocrumb.  Did you try to work with the vendor at all?

 

I use a non-SIPS feather touch.  It works fine.

[Mike Lockwood]

Currently I would want room for no filter, a long-pass or two, a light pollution filter (Celestron), and two different H-alpha filters,3.5nm and 7nm.

 

That's six positions if I needed an empty hole for no filter.

 

Many of my clients use Astrocrumb, including a JPAstrocraft scope with a SIPS that I saw recently.

[a__l]

Who are they?  It's only one person at astrocrumb.  Did you try to work with the vendor at all?

 

I use a non-SIPS feather touch.  It works fine.

They are Starlight and the slider seller. For me was ship one package (SIPS kit + slider) from Starlight.

Twist a slider on SIPS optics, the solution is clearly unsuccessful. As well as others. I will not repeat myself, details are here https://www.cloudyni...wheel-or-slide/

 

By the way, the link is one of the Lockwood optics clients, but he has another sliders (Moonlite + Starlight focuser), 2 telescopes.

Edited by a__l, 16 September 2020 - 10:49 PM.