Date   

Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Worsel
 

This topic has come up on PHD2 forum.  The answer to your question involves more than just the focal lengths now that cameras and software are the norm for guiding.

The OLD rule of thumb when manual guiding was the only game in town was the guide scope focal length had to be at least 1/2 that of the imaging scope.  With the advent of autoguiding, the image scale of the two cameras comes into play.

Bruce Waddington posted some comments about requirements for guide scope and cameras on the PHD Stark Labs forum and copied to PHD2. Note the Stark Labs forum is no longer available

"Hi, this is Bruce.  I posted my response on the Stark Labs forum last night.  As I said there, what probably matters more is the relationship between the two image scales rather than two focal lengths – I think you already knew that.  The goal is for the tracking/guiding to be seeing-limited, you want to keep any centroid error well below that.  Beyond the simple stuff I described, it becomes a matter of your seeing conditions, the sensitivity of the guide camera and how faint the guide star is, the size of the star disks on your main system, etc.   I don’t think there’s any cookbook answer for this.  And if you’re imaging at long focal lengths (fine image scales), the issues of differential flexure will usually take over and most of this other stuff becomes irrelevant."

The following was part of the same thread

Bruce’s approach can be translated into a similar rule of thumb as the historical value with respect to focal length of the guide scope, if we accept a couple assumptions. This reduces the number of calcs needed.

 

GP = Guide camera pixel size in microns

GF = Guide camera focal length in mm

IP = Image camera pixel size

IF = Image camera focal length

 

Assumptions:

    1. Centroid accuracy of 0.2 pixels for the guiding software

    2. Movement of less than 1 pixel on the main image is the acceptable upper limit

 

Guider image scale = GP * 206.265/GF

Imager image scale = IP * 206.265/IF

 

Acceptable Movement on main image = 1 pixel = GP * 206.265/GF * 0.2

                                                                                       ---------------------

                                                                                 IP * 206.265/IF

 

 

 

Rule of thumb

Guider focal length > 0.2*(GP/IP)*IF

 

Bruce’s first example

 

Guider focal length > 0.2*(5.3/7.3)*1680 = 229

The 350 f.l. guidescope is OK

 

Bruce’s second example

Guider focal length > 0.2*(5.3/7.3)*2540 = 354

The 350 f.l. guiderscope is marginal

 

 Bryan


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Roland Christen
 

Yes, you should attach the guider to the imaging scope. I have always recommended that. A separate guide scope on top of the rings will not work because the imaging scope will be flexing inside the rings and be pointing in different directions with gravity.

Rolando

-----Original Message-----
From: M Hambrick <mhambrick563@...>
To: main@ap-gto.groups.io
Sent: Fri, Oct 16, 2020 11:40 am
Subject: Re: [ap-gto] Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Thanks Roland

I am asking because George suggested to me that in order to avoid flexure, I should be doing my guiding with the Baader Vario-Finder attached to the imaging scope rather than to use a separate guide scope piggybacked on top. I already own the separate guide scope and dovetail plates, but I would have to purchase the Baader Vario-Finder. I don't want to buy one if if it is not accurate enough to use with the longer focal length of the 180.


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

CurtisC
 

Mr. Hambrick: At least in earlier years, the recommendation was that the Vario-Finder bracket should be attached directly to the body of the focuser.  My TEC140ED has a Feathertouch 3545 focuser, which has screw holes for the special bracket that A-P sells.  I think A-P's focusers are similar.  The only slightly worrisome part is that the holes are very shallow, and the screws are very short.  They're fine with the Vario-Finder and bracket, but I wouldn't attach anything heavier.


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

CurtisC
 

If Rolando is using the Baader Vario-Finder as a guider on a 175 f/8, then I am well-reassured about resuming use of it on my TEC 140.

Incidentally, Rolando, a fellow Palomar Observatory docent told me you had bought a house in HI north of her.  She lives alternately in Waikoloa Village and Temecula, CA, and she seems to be well-acquainted with Christopher Erickson, who often posts here.  She gave me the name of the community, which I won't repeat here.  I looked in GE for a dome or roll-off, but I haven't found it :)


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

M Hambrick
 

Thanks Roland

I am asking because George suggested to me that in order to avoid flexure, I should be doing my guiding with the Baader Vario-Finder attached to the imaging scope rather than to use a separate guide scope piggybacked on top. I already own the separate guide scope and dovetail plates, but I would have to purchase the Baader Vario-Finder. I don't want to buy one if if it is not accurate enough to use with the longer focal length of the 180.


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Roland Christen
 

I don't know what the limit is. It's not like walking on a pier and when you get to the end you fall off into deep water. It's more like walking into a shallow beach, going further and further out until suddenly your head is under water and the shark is coming. Where that point is, is anyone's guess.

Rolando



-----Original Message-----
From: M Hambrick <mhambrick563@...>
To: main@ap-gto.groups.io
Sent: Fri, Oct 16, 2020 8:40 am
Subject: Re: [ap-gto] Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

I have a question for Roland or George related to one of the previous threads that the Baader Vario-Finder works well as a guider for short focal length scopes. What would you say is the limit of focal length with this finder ? I ask because you have one of these Baader Vario-Finder scopes on your 175 F8 EDF at your Hawaii observatory. 

Will the 10 X 60 Baader Vario-Finder work with a 180 EDT ? I normally use it with a Quad TCC (effective f.l. 1166.4 mm)


Re: ASCOM 6.5?

Ray Gralak
 

There has been a fix to the ASCOM Platform 6.5, but it is still a beta. If anyone needs platform 6.5 and would like to try it here is the link:

 

https://download.ascom-standards.org/beta/ASCOMPlatform65.exe

 

-Ray Gralak

Author of PEMPro

Author of APCC (Astro-Physics Command Center): https://www.astro-physics.com/apcc-pro

Author of Astro-Physics V2 ASCOM Driver: https://www.siriusimaging.com/apdriver

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of George
Sent: Friday, October 16, 2020 7:18 AM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] ASCOM 6.5?

 

Mojo,

 

Go to the Software Update page of our website.

 

Regards,

 

George

 

George Whitney

Astro-Physics, Inc.

Phone:  815-222-6538 (direct line)

Phone:  815-282-1513 (office)

Email:  george@...

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Mojo Jones
Sent: Thursday, October 15, 2020 5:39 PM
To: main@ap-gto.groups.io
Subject: [ap-gto] ASCOM 6.5?

 

I'm moving into a new imaging computer for my Mach1-GTO (early version) with CP3 (current firemware) and APCC pro.

Are we still avoiding ASCOM 6.5? I can't seem to find a download for 6.4 SP1.

Mojo


Re: ASCOM 6.5?

George
 

Mojo,

 

Go to the Software Update page of our website.

 

Regards,

 

George

 

George Whitney

Astro-Physics, Inc.

Phone:  815-222-6538 (direct line)

Phone:  815-282-1513 (office)

Email:  george@...

 

From: main@ap-gto.groups.io <main@ap-gto.groups.io> On Behalf Of Mojo Jones
Sent: Thursday, October 15, 2020 5:39 PM
To: main@ap-gto.groups.io
Subject: [ap-gto] ASCOM 6.5?

 

I'm moving into a new imaging computer for my Mach1-GTO (early version) with CP3 (current firemware) and APCC pro.

Are we still avoiding ASCOM 6.5? I can't seem to find a download for 6.4 SP1.

Mojo

--
Morris Jones, Monrovia, CA
BridgeMojo
Old Town Sidewalk Astronomers
Mojo's Blog


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

M Hambrick
 

I have a question for Roland or George related to one of the previous threads that the Baader Vario-Finder works well as a guider for short focal length scopes. What would you say is the limit of focal length with this finder ? I ask because you have one of these Baader Vario-Finder scopes on your 175 F8 EDF at your Hawaii observatory. 

Will the 10 X 60 Baader Vario-Finder work with a 180 EDT ? I normally use it with a Quad TCC (effective f.l. 1166.4 mm)


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Anis Abdul
 

On Thu, Oct 15, 2020 at 07:52 PM, uncarollo2 <chris1011@...> wrote:
Check your location, (latitude and longitude). If they are mistaken, then these parks will not go where you want.
 
Thank you Rolando! I just checked and Latitude is programmed (00 instead of 30) . Longitude is correct though. I will set that and test! 
Regards
Anis


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Roland Christen
 


I have the same setup CP3/V chip and ASCOM V2 driver does have the position 4 and 5.. The problem is that it just doesn't go to that position .
Check your location, (latitude and longitude). If they are mistaken, then these parks will not go where you want.

Rolando


-----Original Message-----
From: anismo@...
To: main@ap-gto.groups.io
Sent: Thu, Oct 15, 2020 9:21 pm
Subject: Re: [ap-gto] Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Hi KHursh and Mike
I have the same setup CP3/V chip and ASCOM V2 driver does have the position 4 and 5.. The problem is that it just doesn't go to that position .. Very odd. I am not sure if this needs some kind of setup (I just setup the mount in the new observatory and didn't really change anything

I don't use hand controller (it is not connected) and I control the mount just with the PC. 


Thanks
Anis


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Anis Abdul
 

Hi KHursh and Mike
I have the same setup CP3/V chip and ASCOM V2 driver does have the position 4 and 5.. The problem is that it just doesn't go to that position .. Very odd. I am not sure if this needs some kind of setup (I just setup the mount in the new observatory and didn't really change anything

I don't use hand controller (it is not connected) and I control the mount just with the PC. 


Thanks
Anis


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

CurtisC
 

On Thu, Oct 15, 2020 at 04:20 PM, George wrote:
It works great.
FWIW, I looked at the .fits files from projects earlier this year, when I was using the Baader Vario-Finder for guiding instead of the QSI's OAG.  The guiding results were at least as good as what I'm getting now.


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

KHursh
 

I have a 900GTO with a CP3 and V chip. I use the ASCOM driver to set "Park to" and I tell it to park to Park 5. Works every time with SGP or NINA when it's finished with a session.


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Michael Freeberg <snopak@...>
 

I have a CP3 controller and I can go to Park 4.  I have upgraded my hand controller to the latest version and the ASCOM V2. Park 4 shows up in my hand controller and I use it to take my flats.  

Mike

On Oct 15, 2020, at 6:33 PM, uncarollo2 <chris1011@...> via groups.io <chris1011@...> wrote:

The CP3 did not have Park4 and 5 available. Only 1, 2 and 3.

Rolando


-----Original Message-----
From: anismo@...
To: main@ap-gto.groups.io
Sent: Thu, Oct 15, 2020 5:35 pm
Subject: [ap-gto] Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Hi All,

I have been using my AP900GTO with CP3 (V chip) for few years. now and it has been very good. I always used Park 3 position and operated with just SGP and ASCOM driver (not APCC).

I am working on setting up in a remote observatory and I need to set the scope in Park 4 position (For roof park detection and operation). However, whenever I try to use Park 4 (or Park 5), the mount doesn't seem to the horizontal CW position . The RA just swing a small amount and the scope basically. wants to twist 180 degrees. But It goes to Park 3 correctly (Plate-solving etc are all working perfectly).
I have the pretty new  ASCOM V2 (may not be absolute latest but may. be a month old). I cant do user defined park position as well using just the ASCOM driver.

My question is: Do I need to get APCC to get this working properly? I do see park 4/5 as options in the ASCOM driver so I thought it should be working .

TIA and Regards
Anis


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Mike Dodd
 

On 10/15/2020 7:07 PM, Woody Schlom wrote:
Once focused to your guide camera, that should be it. Lock down the
fine-focus with the retaining ring and call it done.
Lock it down is what I do. Some may smile at my method, but it works: <http://astronomy.mdodd.com/observatory.html#Autoguiding>

My 60mm f/5 guide scope no longer has a focuser mechanism, and the camera is bolted to a bracket on a dovetail plate. I loosen the bolt, and nudge the camera while my wife at the computer tells me if focus is better or worse.

It takes about five minutes. I tighten the bolt, and we're done for many months.

Clear skies.

--- Mike


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Roland Christen
 

You can create custom park positions in APCC to point anywhere.

Rolando


-----Original Message-----
From: anismo@...
To: main@ap-gto.groups.io
Sent: Thu, Oct 15, 2020 6:37 pm
Subject: Re: [ap-gto] Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Thank you Rolando. 

If I get APCC, can I use Park 1 as custom park position? I just need it to park in the same spot everytime for park confirmation for roof to close and for flat panel position on the wall.

Best Regards
Anis


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Anis Abdul
 

Thank you Rolando. 

If I get APCC, can I use Park 1 as custom park position? I just need it to park in the same spot everytime for park confirmation for roof to close and for flat panel position on the wall.

Best Regards
Anis


Re: Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Roland Christen
 

The CP3 did not have Park4 and 5 available. Only 1, 2 and 3.

Rolando


-----Original Message-----
From: anismo@...
To: main@ap-gto.groups.io
Sent: Thu, Oct 15, 2020 5:35 pm
Subject: [ap-gto] Park 4 or Park 5 using ASCOM V2 on AP900GTO #ASCOM_V2_Driver

Hi All,

I have been using my AP900GTO with CP3 (V chip) for few years. now and it has been very good. I always used Park 3 position and operated with just SGP and ASCOM driver (not APCC).

I am working on setting up in a remote observatory and I need to set the scope in Park 4 position (For roof park detection and operation). However, whenever I try to use Park 4 (or Park 5), the mount doesn't seem to the horizontal CW position . The RA just swing a small amount and the scope basically. wants to twist 180 degrees. But It goes to Park 3 correctly (Plate-solving etc are all working perfectly).
I have the pretty new  ASCOM V2 (may not be absolute latest but may. be a month old). I cant do user defined park position as well using just the ASCOM driver.

My question is: Do I need to get APCC to get this working properly? I do see park 4/5 as options in the ASCOM driver so I thought it should be working .

TIA and Regards
Anis


Re: Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

Woody Schlom
 

Nick,

 

Once focused to your guide camera, that should be it.  Lock down the fine-focus with the retaining ring and call it done.

 

Woody

 

From: main@ap-gto.groups.io [mailto:main@ap-gto.groups.io] On Behalf Of Nick Iversen
Sent: Thursday, October 15, 2020 3:14 PM
To: main@ap-gto.groups.io
Subject: Re: [ap-gto] Crayford style focuser for Vario-Finder 10x60 ; 61x250 f/4.1

 

I tried the Baader fine focus but in the end I bought a helical focuser which is much easier to use. Screwing and unscrewing the front lens to focus was a pain because it unlocks the lens which has to be locked again.

What is best practice for using the fine focus?

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