Remote Telescope Astronomy Basics
Aussie Pete - iTelescope Observatory Manager
Hello iTelescope.Net Users!
I thought I would pass along a few pointers on just how to maximise your time on a remote telescope and get the most from the iTelescope System.
You would be surpised how many user images I see as part of my duties. I get "Usage Reports" Emailed to me every day from all the systems and they simply amaze me at times.
Most are very pleasing for a support crew to see and give us a great amount of pleasure. Clear focused images and nice round stars. Bliss.
But the odd "Clunker" does reach me on occasion as well. An image with fuzzy and/or trailing stars. I don't like these at all. I pull my hair out at times like this. What to do? My process goes something like this:
- I check the user's Log during the image
- I check the weather during the time of the image
- I check the targets Altitude
- I check for proximity to a bright Moon
- I check the image exposure time
- I check other images from just before and after the user's own session
- I check the sugar levels in my coffee
- I check the telescope system logs for faults during focus, guidance or pointing subroutines
- I check for any possible faulty calibration frames involved
- I check to see if our technician is awake for a fast Skype consultation
- I check all this then I keep an eye on that system for a while
During this routine I usually can find something to pin the blame on. A focus or guiding failure caused by cloud, wind, roof closure due to weather, close proximity to a bright Moon, frozen fog or a system error that can lead to a telescope crashing and burning. Well not quite burning, but its a bad thing.
Yet a system failure can also be a positive, when we can correct it and prevent it from occurring again. This is why sending us a prompt Support Message or even an Urgent Page to our phones (see link on LaunchPad) can be very helpful to all involved.
A nearby bright moon can effect a session in several ways. The telescope may not be able to find a guide star or focus properly. Moonglow can also washout an image if its too close, making the saved calibration data ineffective or cause reflections within the telescope optics. We suggest you give a bright moon at least 60 degrees clearance. This is where a good planetarium application comes in handy. Narrowband filters will negate the moon nicely as well.
Telescope FOCUS and GUIDING can be effected by a number of factors.
Its easy to blame the telescope when your images just dont look as good as they should. But dont be too hasty, are you asking the telescope to do too much during poor conditions? Would you pop out and stargaze during a cloudy or windy night? Have you checked the All Sky Cameras and weather at the remote site?
Part of the remote telescope's initial starting routine is to automatically slew or move to a designated focus star. It will try to center this star in order to get the most accurate focus it can. It will take a short exposure of the general area and then precisely move a small amount to get its target star centered.
Then it will focus itself and when done move on to the target for your session.
BUT, if its slightly cloudy during this very important phase, and these 'pointing' or 'Plate Solving' images are poor, then firstly the telescope will not know exactly where it is, AND it will not be able to carry out its focus routine to its best or to full completion.
It will try several times to carry out this pointing/focus phase, then give up and do its best to approximate the focus needed (going by its last recorded, earlier focus position) and then slew to your target area for the night. Again it will try to center your target by taking a short image and calculate a small pointing adjustment or plate solve, but if its cloudy in the target region again, it WILL miss the target by some amount depending where in the sky your target is.
This can be annoying if your aim is to 'stack' a number of sub exposures in astro imaging or need critical positioning. The results can be off target AND poorly focused images. Nobody wants that. So try again another night.
Then to make matters even more difficult for your remote telescope it may also need to guide on a star during your session. If it cannot find a star due to cloud or the star fades behind cloud during a long exposure, then the image could be effected, not least by the passing cloud itself. Take care with partly cloudy weather.
At times a crowded star field can also play havoc with the guider. The 'intelligent' guidance software we use (MaximDL) sometimes picks a guide star with close companions. The guider will 'bounce' between the two or more stars in the field of view. Annoying but thankfully rare. This can lead to 'zig zag' guider errors. Not much can be done except aborting your session and restarting, hoping the SW will pick a lone star next time round.
Astronomical Seeing is another factor that can really effect your remote telescope session.
When the local atmosphere above the observation site is unstable or turbulent this can result in 'soft' focus and shaky guide stars. Seeing conditions can change rapidly during a night, even moment to moment, so if your images do look a little soft or the guider is wandering around this can be the cause. Not much can be done about seeing but its something to be aware of. The telescope is doing its best to do its job for you. While seeing does not really effect science missions, it can be a real problem for imagers.
Windy conditions at the remote sites can at times cause tracking errors, this is a rare occurrence, but sudden gusts can and will effect some of the telescopes. The result can be slightly egg shaped stars or blurred images. At times like this the domes usually shut automatically.
Foremost on my mind is the telescope user. Apart from a waste of points and time, they have possibly lost a time critical observation or a chance to image something really special. I can understand the frustration they must feel when a horrible mess appears on the preview screen or in the Email or their FTP folder. What to do?
Well the majority of the time our more experienced drivers know exactly what went wrong and they correct the flaw in the plan and carry on, but what of those not so accustomed to remote telescope imaging? They may indeed get a very bad impression of our systems and telescopes in general.
They deserve the best we can deliver to them as far as internet astronomy goes.
So apart from my investigations and the odd refund, what can an iTelescope user do to avoid frustration and spamming iTelescope support? A few simple and easy steps can do the trick for you.
- Plan your remote telescope session carefully
- Check the weather often
- Understand the remote telescope
- Testing the system before you start a very long session
- Be Patient with the telescope
- Dont be shy and Contact Support if you feel the need
- Yes, we can return points that are wasted for whatever reason
Planning means knowing your target is at a favourable elevation and at least 60 degrees from a bright moon. Science users dont need to worry so much about moonglow. Having a planetarium program really is vital.
Weather needs to be monitored. We provide numerous links to our weather data and wide angle Sky Cameras. SO USE THEM! Refresh often and be aware.
Understanding a remote telescope means knowing its limits and strengths. At times you will want a wide Field of View (FoV) and a fast f ratio. Others a more narrow and close up view of your intended target. I would not recommend a new user chasing a comet or fast moving NEO asteroid with T4's narrow FoV for example. T14 would do the job much better and more easily.
Guider & Tracking Limitations.
Many of the older iTelescopes use external guide scopes (Pararmount PME mounted - Check via the telescope info pages) in which case there is a limit on reliable guidance. An external guidescope will effect how long you can reliably track a target without slight errors creeping into the image resulting in slightly egg shaped stars etc due to unavoidable 'flexure' between the guidescope mount bracket and the main telescope. Try and keep your exposures under 600 seconds in this case. Ideally 300 seconds. If you need extra signal then try several sub exposures at Binx2 & 300 seconds instead. All of the larger and newer Planewave Ascension mounted itelescopes can go 600 seconds with ease.
More information can be found if you log into a telescope (no charge until you start to image) and click the “Telescope Info” link to the bottom left. It shows the telescope field of view (FoV), CCD type, filters assignments etc.
Also try to avoid use of overly long exposures in one single shot. It actually gains you very little in detail or depth. The way a CCD works your much better off using a series of shorter shots and stacking them to increase your signal.
iTelescope recommends you limit your exposure to 300s or less.
I have seen images attempted on our systems of over 7000 seconds! Not good. Your images will be subject to guiding errors, passing cloud, wind, satellite tracks, cosmic ray strikes, climate change etc.
iTelescope suggests exposure times of: 60, 120, 180, 300 or 600 seconds. We have matching calibration data for these times.
Testing the System means just that, its optional, but worth while if you have a long session in mind. Before you trigger a long sequence of multi-filter shots, test that the telescope is in good order. It does not take long and often will save you having to start again if things do go a bit wrong. Support does check every telescope before the domes open but we are dealing with very complex equipment and software so gremlins can sneak past our security now and then. If you do find a problem let Support know as soon as you can.
- Check the SkyCams!
- Check the elevation and position of your target. (Is the moon very close? Is my target above the low limits of the telescope of 25-35 degrees)
- Input your target in the ACP interface
- Set up a 30 second exposure with a Clear or Lum filter
- Watch the System Status readout during the test
- Check the Jpeg preview for quality
- Check the SkyCams again!
Did everything work well? To center the object for stacking later, may we suggest not using the 'Express Mode'. The other modes will 'plate solve' the field of view and then precisely position the telescope, albeit at a small time overhead, before starting your image sequence.
Great! Now your ready to start that epic imaging session.
Go back and input your sequence. Check its what you want then hit "Acquire"
Be patient with the system as it does its job. Autofocus and Pointing subroutines can take some time to achieve. The telescope will try to find the best guide stars and focus candidates to work with. In a depleted star field this may take a few minutes and while the system status may Appear to be doing nothing at times due to internet lag etc, it is working hard in the background to give you the best result. But if your in doubt, send us a SUPPORT email.
But dont forget, CHECK the WEATHER! Keep an eye on the SkyCams. Abort if you feel its getting scary, you can always try or continue again later. Contact Support if your not happy with the results of your session as soon as possible too. We are happy to return your points.
There you go. Before long you will become accustomed to using a remote telescope on the other side of the world, something professional astronomers do every night and now you can call yourself a real pro!
You can also find useful guides here: