Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

Stupid filter question

  • Please log in to reply
7 replies to this topic

#1 John Tucker

John Tucker

    Viking 1

  • *****
  • topic starter
  • Posts: 867
  • Joined: 03 Mar 2018

Posted 24 May 2019 - 09:08 PM

I have a LX200 8 inch SCT which I've used with both a standard 1.25 inch T adapter and with a wide bore adapter sold by Meade https://www.adorama....ource=adl-gbase,

 

I've ordered both 1.25 inch and 2 inch threaded adapters and they don't screw in anywhere in this optical train.  

 

Dumbest question in the world: How do you fit the filter between the camera and the OTA?  Everything is threaded but the threads don't match up.  

 

I asked Highpoint about this and they tried to sell me a filter that clips into the body of my Canon, but it seems crazy to me that with all these threaded parts I can't buy a simple threated filter that screws into the adapter or the back of the OTA. 

 

Looking into narrowband now and since these filters are expensive I don't want to figure this out by trial and error. 


Edited by John Tucker, 24 May 2019 - 09:12 PM.


#2 ngc7319_20

ngc7319_20

    Apollo

  • *****
  • Posts: 1014
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 24 May 2019 - 10:16 PM

Usually a 1.25" filter can be threaded on to a 1.25" / T adapter.  But maybe your adapter does not have threads?


  • John Tucker likes this

#3 RogeZ

RogeZ

    Apollo

  • *****
  • Posts: 1086
  • Joined: 21 Nov 2004
  • Loc: Palm Beach Gardens, FL

Posted 24 May 2019 - 10:37 PM

Filters should never be load bearing unless design to be so like SCT body filters. All others should go on a filter drawer or wheel.
  • pgandy and John Tucker like this

#4 Stelios

Stelios

    Cosmos

  • *****
  • Moderators
  • Posts: 7700
  • Joined: 04 Oct 2003
  • Loc: West Hills, CA

Posted 24 May 2019 - 10:52 PM

Do you have a 2" filter? Does it not thread to the inside of your T-adapter? 

 

Typically solutions for DSLR's (which, judging by the Meade T-adapter you show, is what you need) will accommodate light-pollution filters, but are usually not designed for narrowband filters. Buying 2" narrowband filters to use with a DSLR doesn't make financial sense--the 2" filters will cost significantly more than the DSLR...



#5 44maurer

44maurer

    Viking 1

  • *****
  • Posts: 578
  • Joined: 12 Jun 2016
  • Loc: Los Angeles, CA

Posted 25 May 2019 - 02:14 AM

Do you have a 2" filter? Does it not thread to the inside of your T-adapter? 
 
Typically solutions for DSLR's (which, judging by the Meade T-adapter you show, is what you need) will accommodate light-pollution filters, but are usually not designed for narrowband filters. Buying 2" narrowband filters to use with a DSLR doesn't make financial sense--the 2" filters will cost significantly more than the DSLR...


+++1

#6 John Tucker

John Tucker

    Viking 1

  • *****
  • topic starter
  • Posts: 867
  • Joined: 03 Mar 2018

Posted 25 May 2019 - 10:21 AM

Do you have a 2" filter? Does it not thread to the inside of your T-adapter? 

 

Typically solutions for DSLR's (which, judging by the Meade T-adapter you show, is what you need) will accommodate light-pollution filters, but are usually not designed for narrowband filters. Buying 2" narrowband filters to use with a DSLR doesn't make financial sense--the 2" filters will cost significantly more than the DSLR...

So here is the 1.25 filter screwed into the end of the nose piece for my little $100 planetary camera.  No problem here.  But you're saying I can't do this with a narrowband filter?

 

Capture.JPG

 

For the DSLR adapter, the 1.25 inch is far too small.  If I put the 2" filter on the end of the adapter that connects to the OTA, it protrudes too far radially and prevents attachement to the OTA

 

Capture - Copy.JPG

 

If I attach it to the other end, it screws right in but now it protrudes too far axially and the adapter cannot be screwed into the camera

 

Capture2.JPG

 

I just bought a PowerNewt and a very inexpensive used astrophotography camera (Meade DSI, 0.25 megapixels) with the idea of picking up a lower priced Ha filter and trying this out.  I also picked up this filter drawer.

 

https://www.teleskop...ngth-15-mm.html

 

Did I screw up?



#7 ngc7319_20

ngc7319_20

    Apollo

  • *****
  • Posts: 1014
  • Joined: 25 Oct 2015
  • Loc: MD

Posted 25 May 2019 - 12:40 PM

Besides 1.25" and 2" filters, they also make SCT back filters.   I guess this is why they make them -- to solve this exact problem.  However I see them less and less these days.

 

The other way out of this, is to get a 2" back for your SCT, get a T-2" adapter for the camera, and then put your 2" filter on the 2" adapter.

 

Baader makes lots of adapters.  Here one scheme with a 2" filter mounted on the back of an SCT...

https://www.baader-p...extension).html

 

Borg / Hutech / IDAS also make lots of adapters. They make a 48mm/2"  light pollution filter that will screw on to the back of your SCT and then has a male SCT thread you just attach your normal SCT stuff on to:

https://www.firstlig...daptor-set.html

https://www.sciencec...ters/fltsct.htm

But you can also buy it without the filter.  The you could just use your existing 2" / 48mm filters on the SCT.  You would need Borg parts 7424 and 7502

https://www.sciencec...s/html/7424.htm

https://www.sciencec...s/html/7502.htm


Edited by ngc7319_20, 25 May 2019 - 12:55 PM.


#8 John Tucker

John Tucker

    Viking 1

  • *****
  • topic starter
  • Posts: 867
  • Joined: 03 Mar 2018

Posted 25 May 2019 - 12:57 PM

Besides 1.25" and 2" filters, they also make SCT back filters.   I guess this is why they make them -- to solve this exact problem.  However I see them less and less these days.

 

The other way out of this, is to get a 2" back for your SCT, get a T-2" adapter for the camera, and then put your 2" filter on the 2" adapter.

 

Baader makes lots of adapters.  Here one scheme with a 2" filter mounted on the back of an SCT...

https://www.baader-p...extension).html

 

Borg / Hutech / IDAS also make lots of adapters. They make a 48mm/2"  light pollution filter that will screw on to the back of your SCT and then has a male SCT thread you just attach your normal SCT stuff on to:

https://www.firstlig...daptor-set.html

https://www.sciencec...ters/fltsct.htm

But you can also buy it without the filter.  The you could just use your existing 2" / 48mm filters on the SCT.  You would need Borg parts 7424 and 7502

https://www.sciencec...s/html/7424.htm

https://www.sciencec...s/html/7502.htm

Cool, thanks!  I don't understand why those things would be made with such similar but non-identical threads or how you look up online what piece has what thread, but it looks like you've set me up for now.


  • ngc7319_20 likes this


CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.


Recent Topics






Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics