Hi John,

Thanks for your response. By now most of our users should know we are always interested in hearing the unvarnished truth as it applies to each individual’s unique experiences at GRAS. We only ask that it be in the form of frank and critical terms presented in a constructive manner.

To better understand the operation of ACP, please consider it was originally designed to provide an individual owner/operator of an observatory an option to automate their respective observing activities and possibly share access with a few other observers. If you can visualize the manner in which it functions from that perspective then one can quickly see why GRAS users at first see the operations so differently.

Our decision to implement ACP at GRAS is based on my personal experience; under my tests, ACP has proven to be extremely robust and reliable. Also it is extremely powerful in its ability to simplify many of various types of individual activities undertaken by many of our observers.

One of the tradeoffs is that there are many new features to use and therefore learning how to address these features to one’s advantage takes a bit more practice. However as I have attempted to point out in the videos, the simple features are there to use so one need not get deeply involved in the more complex features until one is ready for them.

Also my recent observations of some of our users sessions have led me to conclude that some of our observer’s attempts to use ACP have not allowed for the fact that the weather conditions were less than conducive to producing acceptable results. Autofocus will not work if there are no stars available on which to focus. So when you invoke the system to focus and there are clouds blocking the access to the stars it is not surprising that the focus operation will fail and also flail around quite a bit in the process this is certainly predicable behavior since the focusing algorithms are extremely robust and tenacious.

John, while I appreciate all the painstaking efforts you put forth to plan your mission in using G3, none of this would have even been necessary had I seen fit to anticipate factors enumerated below and had installed an external guide scope to begin with. 

based on my analysis of the situation here is my view the elements involved in currently inhibiting G3’s ability to perform as a suitable platform from which the take narrowband filter images. (Just as a side note, the LRGB filters all support the internal chip guiding functionality as expected).

1. F7 optical speed
2. five or 6 nm bandwidth
3. Smaller field of view
4. Smaller aperture
5. The color of the guide star selected with respect to the rejection factors of the narrowband filters

The three elements identified above, all contribute to the lack of suitability for narrowband imaging using the internal guide chip. The slower optical speed, narrow bandwidth of the filters and smaller field of view, all inhibit the ability to find a suitable guide star.

The addition of an external guide scope will resolve all of the issues above.  Contrary to the view you expressed about external guide scopes the success of this technique has been consistently demonstrated on G1 and G2 for several years now. 

Just to address your concerns directly, we expect to have an external guide scope installed on G3 within a few days. Once this is accomplished, you will rarely need to be concerned with the position of guide stars or anything else, because the field of view will be large enough to almost guarantee a suitable guide star will always be available.

Now the other issues about composition, the resolution of the preview images and centering in moving the objects around all been addressed in a my previous newsletter published on the 17th. For your convenience, here is a link.

Thank you again for taking the time to comment and add your point of view. We appreciate your direct and Frank discussion based upon your personal experience.

we would also like to thank you again for your extensive activities at GRAS; we sincerely appreciate your many contributions.

Arnie

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From: Rent-a-scope@yahoogroups.com [mailto:Rent-a-scope@yahoogroups.com] On Behalf Of aspen6lane
Sent: Wednesday, July 18, 2007 8:47 PM
To: Rent-a-scope@yahoogroups.com
Subject: [Rent-a-scope] ACP modifications

Hello Arnie and GRAS Team,

I have some thoughts to share in regard to a modified ACP program,
if that's what you are considering for GRAS scopes. As you know,
night before last I could not get ACP on GRAS3 to recognize selected
guide stars through the Ha filter on two targets even though I had
painstakingly pre-planned the shots in Starry Night using both ACP
Planner and the current position angle of the guide chip to obtain
the proper coordinates of the field of view center. Unfortunately
with ACP there is no visualization of the guide chip image, so you
have no idea of the problem's source, if it does not work. Could it
be wrong coordinates, wrong pointing (unlikely with plate solving),
guide star not bright enough or centered enough? Maybe ACP requires
a brighter guide star than Browser Astronomy (BA) does? Although
one solution, as Arnie suggests, is to use an external guide scope
with ACP on GRAS3, as it exists now we still would not be able to
see the guide chip image and "know" that our coordinates and
position angles were correct and that there is a guide star
present. Might there be a way to see the guide chip image (as there
is in BA)? Speaking of visualization, the preview image and end of
exposure image provided by ACP is not good at all – the enlarged
version is worse! Why is this ACP image so inferior to
the "centering" image in BA? One possible way of getting around not
seeing the guide chip image is to have a good preview image from the
main chip (with a centering cross hair). The "centering" image from
the main chip is what I typically use in BA to move the scope to a
pre-planned FOV center for both composition and for placing a star
on the guide chip. Unfortunately, the preview images in ACP are so
bad that I cannot see the individual stars and nebular details that
I use for FOV centering! Plus in ACP there is no simple way
to "tweak" the image position without entering a full set of new
coordinates. There is no "click where you want to center" or move
so many minutes in a given direction as there is in BA. External
guide scopes have been tried before on RAS scopes and later
determined not to be a great answer ( I think because of
differential flexure). Is the real problem related to hardware,
namely that of guide chip insensitivity with narrowband filters?
That I doubt because I have previously guided successfully with the
same narrowband filters with equally dim guide stars with GRAS 3, 5,
6, and 8 using BA software or whatever combination software is used
on "BA" systems.

I am all for progress, but many of the "black box" automated
features of ACP provide little solace when they do not work. I'd
rather know what I did wrong, so not to do it again. Are there ways
to get better feedback on what ACP is doing, particularly in regard
to quality visualization of the FOV of both main chip and guider?

As you well know, my intent is that these comments are helpful and
not hurtful.

Regards,

John

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