Back Spacing Again - Sorry


Emilio J. Robau, P.E.
 

I can't find a post I read a few weeks ago on the best way to dial in back spacing.   I think Roland posted a methodology for dialing in the spacing that had to do with the focus point.   Can anyone help me find that post.  Thanks in advance for any response.  I thought I had bookmarked it, but I can't find it.  At this moment my stars on my home brew newt with a Wynne corrector show crosses.   I want to know if I need to reduce distance or increase distance.  I am close.  Thanks for any reply.   The scope is on an AP1100 so I thought I would throw that in for relevance and standing to post on this forum.

Thanks


Chris White
 
Edited


Emilio J. Robau, P.E.
 

Thanks.


ap@CaptivePhotons.com
 

If you are a NINA user (and as Chris mentions in his note), the Hocus Focus tool is really pretty good with both backfocus and tilt, doing a quantitative analysis to suggest both direction and (for tilt) amount of movement.  I've had mixed results with tilt, I think primarily because it is just difficult to physically move a few microns on one corner, not software limitations. But backfocus measurement with it has been spot on.  Just find a really dense star field without a lot of nebulosity, you need a lot of stars on all the corners.  Also, run the same setup a couple times as you go (no physical adjustment) to see how repeatable it is, so you aren't chasing seeing differences.

Linwood


Emilio J. Robau, P.E.
 

In building my Newtonian, I have come to the experience realization as to why people just like refractors.   There have been several instances where I seriously just thought of taking the scope apart and selling the parts.  However, I am almost there.   I am dealing with some tilt and backspacing issues.  Alignment and collimation appear to be correct.   I still have to get the diffraction spikes adjusted by adjusting the spider vanes. So, I realize why people just like refractors. 

However, I have not given up and am almost there.

I also realize how nice a simple Newtonian can perform if correctly aligned and corrected.  The other day I took the thing off the 1100 and just decided to switch out to my ES127 FCD 100 scope with an AP27TVPH, which is my place holder hoping that AP will place the 130 back into production and my name will be called.   After tweaking everything, the image looked okay, but honestly it forced me back to trying to salvage the home brew Newtonian which with all it's imperfections looked less murky than the ES.  It was actually sharper.

So, I went back to the Newt and had some success and am hopefully working only on Tilt, and back spacing.  I also have to adjust the vanes, but I have it well collimated in the center field of view now and will try to get the tilt out and the backspacing correct before I adjust the vanes.

My Stowaway is pure joy.  Sharp stars to the edge on and APS-C chip.  Easy thing to do with such a precise instrument.  I just love it.   Hoping AP will put the 130 back into production and my name gets called.   I have been on the list since 2017.  I got lucky with the Stowaway lottery.   I have missed two brand new second hand 130s over the past three months.

Back to the Newt.


Roland Christen
 


Hoping AP will put the 130 back into production and my name gets called.
The 130 is in continuous production. It takes many months to work thru all the steps to make lenses, plus it takes a lot of time in machining and finishing to produce the mechanical parts.

Rolando

-----Original Message-----
From: Emilio J. Robau, P.E. <ejr@...>
To: main@ap-ug.groups.io
Sent: Tue, Nov 29, 2022 10:55 am
Subject: Re: [ap-ug] Back Spacing Again - Sorry

In building my Newtonian, I have come to the experience realization as to why people just like refractors.   There have been several instances where I seriously just thought of taking the scope apart and selling the parts.  However, I am almost there.   I am dealing with some tilt and backspacing issues.  Alignment and collimation appear to be correct.   I still have to get the diffraction spikes adjusted by adjusting the spider vanes. So, I realize why people just like refractors. 

However, I have not given up and am almost there.

I also realize how nice a simple Newtonian can perform if correctly aligned and corrected.  The other day I took the thing off the 1100 and just decided to switch out to my ES127 FCD 100 scope with an AP27TVPH, which is my place holder hoping that AP will place the 130 back into production and my name will be called.   After tweaking everything, the image looked okay, but honestly it forced me back to trying to salvage the home brew Newtonian which with all it's imperfections looked less murky than the ES.  It was actually sharper.

So, I went back to the Newt and had some success and am hopefully working only on Tilt, and back spacing.  I also have to adjust the vanes, but I have it well collimated in the center field of view now and will try to get the tilt out and the backspacing correct before I adjust the vanes.

My Stowaway is pure joy.  Sharp stars to the edge on and APS-C chip.  Easy thing to do with such a precise instrument.  I just love it.   Hoping AP will put the 130 back into production and my name gets called.   I have been on the list since 2017.  I got lucky with the Stowaway lottery.   I have missed two brand new second hand 130s over the past three months.

Back to the Newt.


Emilio J. Robau, P.E.
 

Roland,

Thanks for answering my back door question.  I was concerned that the 110 would trump the 130, but alas it may not and I will sign up for the 110.  Hope everything is well for you in Hawaii.  I also have a second place next to a volcano.  However, when Yellowstone blows, it will be a little different.   


M Hambrick
 

Great article Chris.

Is the Astrobin forum copyright protected ? I was thinking it would be nice to convert your article into a Word document that users can download to keep where they can find it again.

Mike


Chris White
 

Mike,

Well, since I'm the author I can do what I want.  🙃

Here is a guide with the important sections from that thread.  Let me know if this is what you are looking for. 

https://ap-ug.groups.io/g/main/topic/guide_to_fixing_tilt_and/95343845?p=,,,20,0,0,0::recentpostdate/sticky,,,20,2,0,95343845,previd%3D9223372036854775807,nextid%3D1669039538557137734&previd=9223372036854775807&nextid=1669039538557137734


ROBERT WYNNE
 

With regard to Hawaii I understand shelf integrity is also a problem with simultaneous eruptions. Hard to imagine the caldera is full. I'm fairly safe over in Kauii. -Best, Robert 

On 11/29/2022 9:27 AM Emilio J. Robau, P.E. <ejr@...> wrote:


Roland,

Thanks for answering my back door question.  I was concerned that the 110 would trump the 130, but alas it may not and I will sign up for the 110.  Hope everything is well for you in Hawaii.  I also have a second place next to a volcano.  However, when Yellowstone blows, it will be a little different.   


ROBERT WYNNE
 

In all the intellectual property litigation I've been involved, copyright only comes into play when the author has been duped by income stolen by the plagerist no matter what the law may say. If there are no damages why bring a lawsuit other than to soothe a bruised ego, incur legal expenses and the courts/attorney's time? -Best, Robert

On 11/29/2022 11:04 AM M Hambrick <mhambrick563@...> wrote:


Great article Chris.

Is the Astrobin forum copyright protected ? I was thinking it would be nice to convert your article into a Word document that users can download to keep where they can find it again.

Mike


M Hambrick
 

Hi Chris

Thanks so much for the article. It looks like you went to a lot of trouble to make that document. I really didn't intend for you to go to that much trouble. If you had said it was OK, I would have copied the information into a Word document.

Thanks again.

Mike


Chris White
 

On Wed, Nov 30, 2022 at 05:53 AM, M Hambrick wrote:
Thanks so much for the article. It looks like you went to a lot of trouble to make that document. I really didn't intend for you to go to that much trouble. If you had said it was OK, I would have copied the information into a Word document.
It was no trouble. Took maybe 20 min. I knew where the important sections were so just cut and pasted. I might revise at some point but this is just a cut and paste job to help folks zero in on the info.