iEQ45 PE reduced to 4.5 arcsec peak to peak!!
Posted 24 February 2013 - 10:45 PM
After looking at other users results in which the PE of iEQ45 mounts has been taken to +/-2 arcsec, I decided to try with mine. Those results have been published in the iEQ45 imaging yahoo group.
My mount is an iEQ45 of the first batches with 8406 hand control. I used a trial version of Pempro to measure the Periodic Error (PE) of the mount and found it was 14.38 arc-secs: http://flic.kr/p/dXEmxd . Better than expected.
Data was aquired through a Celestron C6 SCT with an Orion StarShoot Autoguider and a Celestron f6.3 focal reducer. Pixel Scale was 0.95" per pixel, which implies the telescope was at f7.5 (1130 mm).
After training the Periodic Error Correction (PEC) on the mount, I got a peak to peak PE of just 4.59 arc-secs: http://flic.kr/p/dXyEEX
This is a very satisfying result which speaks very well about this mount!
Posted 25 February 2013 - 07:52 AM
These results show than in fact the iEQ45 performs very well when compared to other mounts in its class.
I must clarify that in no way I'm related to iOptron. I'm just a satisfied costumer.
You have very valuable information in that list. A good guide about mounts performance.
Posted 25 February 2013 - 10:04 AM
Posted 25 February 2013 - 03:47 PM
I think I'm going to run PemPro tonight on my mount. Quick question though. In the setup for the mount it asks you how many teeth are in the worm gear. I found the number 216 on iOptron's website for mount specs. Is this the correct number of teeth?
Posted 25 February 2013 - 05:25 PM
Posted 25 February 2013 - 05:45 PM
Yes, that's the correct number of teeth
Thanks for the info!
Posted 25 February 2013 - 06:22 PM
Keep us posted about your results.
By the way what's your name?
Posted 25 February 2013 - 06:38 PM
Posted 25 February 2013 - 11:00 PM
You may still be able to do it by using Ascom thru the RS232 port to guide instead of the ST4 port?
Posted 25 February 2013 - 11:13 PM
Posted 26 February 2013 - 07:23 AM
Since I own the 8406 HC and not the 8407, I couldn't tell. Nevertheless that has been said in the iEQ45 imaging Yahoo User Group and yes, you can guide through the serial port with PEC on.
I think with 8406 you can guide with PEC on through the standard ST4 port. I can check that next time I am under the stars
Posted 26 February 2013 - 07:40 AM
I couldn't get PEMpro to work. I have the older controller. I was using my guide camera to try to get it work, an Orion SSAG.Which is plugged into the the ST4 port and then USB'd into my computer. It was not recognizing the mount. Should I have had the RS232 cable plugged from the mount into the computer as well or is that guide scope setup enough? Also what other software do I need for PEMpro to work? Thanks!
I also have the "older" 8406 controller and this seems to be an advantage because it would let you guide through ST4 port with PEC on.
To make Pempro work, you need to use the SSAG as your main camera in Maxim (check Pempro's help because I think other software also will work). Then you run the tutorials to configure everything. I may be wrong, but you can't connect the SSAG to the ST4 port for this process.
There are some settings you need to configure. See here
Posted 26 February 2013 - 08:43 AM
Thanks for the help again. I'll try it today and see if I can PEMPro to work. It's going to be raining/snowing the next few days so I went be able to test under the skies until then.
Posted 26 February 2013 - 02:43 PM
I think with 8406 you can guide with PEC on through the standard ST4 port. I can check that next time I am under the stars
Thank you Alfredo,
Just an update for 8407HC users, iOptron has informed me that PEC will indeed work in conjunction with ST4 autoguiding...?
“The autoguiding will work as long as the mount is in tracking. If the PEC is ON, they will work together. The PEC playback period is 0.1 second. If autoguiding period is greater than 0.1 second, the PEC will play the main role.”
I had a little concern about the 'as long as the mount is tracking' statement. Does that mean just visually tracking an object?
And, if the PEC playback is .10 sec..then you would have to have your PHD exposures at .05 seconds, to enable PHD to send guide commands..and that won't work at that short exposure unless you're guide star is Sirius or another very bright star.
So, next opportunity I have with the iEQ45, I'm going to try and record PEC and initiate playback, with, and without guiding enabled, just to see what's going on.
If any other 8407HC users have successfully used PEC in tandem with ST4 port guiding, I'd love to hear about it.
Posted 26 February 2013 - 06:06 PM
Wow that opens up a lot more questions??!! LOL Good to know the PEC period though. Since it's that short more reason to collect a lot of curves and average them in PEMPro.
Posted 27 February 2013 - 12:45 PM
I'm very happy with my mount, as well as others who have gotten similar results
Posted 27 February 2013 - 10:09 PM
On paper, the iEQ45 looks very promising. Load capacity is enough for a 9.25" SCT which is the heaviest telescope I will ever want to handle. Price is moderate. Weight, which is my major concern, is substantially less than an Atlas or CGEM. However, I have been discouraged by comments about uncorrectible tracking errors that would make the mount useless at focal lengths greater than a few hundred millimeters. At this point, I can't decide whether to buy an iEQ45 as my permanent imaging mount or to start out with something cheap, like a CG-5, to learn with, and make the big financial jump to the likes of an Astrophysics Mach1 later on.
I would like to propose the following test of an iEQ45's tracking accuracy. Track on and photograph a bright star such as Sirius. Use a long focal length to magnify the results of tracking errors. An SCT with a Barlow instead of a reducer would be a good choice. Make repeated images, as quickly as possible, for at least one full worm period. It may be possible treat the star like a planet and run a DSLR in video mode. Perform the test with all four combinations of PEC on and off and autoguiding on and off. Examine the images and graph the movement of the target star over time.
With autoguiding off, I would expect to see the results Alfredo got superimposed on a steady drift due to residual errors in polar alignment. With autoguiding on, I would expect to see the drift eliminated and hope to see the remaining PE substantially reduced. What are of most interest are tracking errors that autoguiding, with or without PEC, cannot correct. They are what determines the longest focal length at which one can still get good images. I have read comments that a Mach1 has a PE of 0.5 arc-seconds out of the box. This is impressive but irrelevant if one can do as well autoguiding an iEQ45.
Posted 27 February 2013 - 10:49 PM
Posted 28 February 2013 - 12:46 AM
As a beginner, I am confused by the extreme range of recommendations I have found on various forums. There are people who are happy with a C8 on a CG-5. On the other hand, when I asked, elsewhere, about a Losmandy GM-8 versus a G11 to carry a C9.25, a couple of responses stated that both the mount and the telescope would be a disappointment and that I would be better off jumping straight to Astrophysics or Takahashi equipment. There seems to be consensus that mount capacity ratings should be discounted by 30% to 50% for astrophotography. Yet a guy in my local club is doing well with a C11 plus camera and piggy back guide scope on a CGEM. The CGEM's 8/3 issue and the C11's mirror shifts don't appear to cause him problems. It has been recommended that I begin at an image scale of no less than 2 arc-seconds/pixel. At that scale, the Ring Nebula occupies only 75 pixels. Rather than start with something small and cheap and upgrade repeatedly until I find a satisfying combination of mount and telescope, I would prefer to do enough research to jump straight to the final one.
Posted 28 February 2013 - 07:06 AM
Generally speaking, the smaller the mount, the bigger the load, and the longer the focal length, the worse the results. And, as you've read, a good rule of thumb is that you should load a mount between 50% to 70% to get the best results. But again, some people are perfectly happy with the results even when exceeding those numbers, some times by a lot. And then of course there's the variation in the quality from example to example of the same mount.
So if you're looking for hard answers, you won't find them. Unless you're already in the game and have tried several mounts and know your own tolerance for quality level in your images, all you can do is go by the "rules of thumb".
A C8 will work on a 30 pound capacity mount like a CG-5, VX, Sirius, iEQ30, or HEQ5. But, when you add up the weight of all gear you'll have mounted along with it, it will be much happier on a 40-45 pound capacity mount like an Atlas, iEQ45, or CGEM. A C9.25 is starting to push that 40-45 pound mount class, but will certainly work on it. I think a C11 is too much and should be on the next class up with a 60 pound or more capacity, but again, there are those who will do it and be satisfied with the results.
Posted 28 February 2013 - 07:45 AM
It has been recommended that I begin at an image scale of no less than 2 arc-seconds/pixel. At that scale, the Ring Nebula occupies only 75 pixels. Rather than start with something small and cheap and upgrade repeatedly until I find a satisfying combination of mount and telescope, I would prefer to do enough research to jump straight to the final one.
Hi and welcome to cloudy nights.
You have a refreshingly open perspective on the issues of autoguiding and PE, and I agree the information you find on the web can be confusing. For some reason there is a strong emphasis placed on the PE characteristics of a mount - when that is separate from how well the mount can create a small image of a star when autoguiding - which is the whole goal of good autoguiding in the first place.
In short, when you hear advice I would look at the actual results people get with the equipment they have. There are many plots showing a reduction of PE, but it is rare to see information on a corresponding reduction in star size, or fwhm in arc-seconds. There are many people who could not get good results with mid-range equipment and found a dramatic improvement spending for high end - but that doesn't mean they could not have achieved similar results with mid-range using the right techniques and software.
This leads to advice not to bother with mid-range equipment, and discouragement that small stars can ever be obtained - hence a push towards large pixels. There is no doubt that a small refractor and big pixels, in arc-seconds, is easier for imaging - but if you want high resolution in something like the ring nebula - then you will need long focal length and small pixels, in arc-seconds - but the result is achievable as demonstrated by many people, including my images on the MetaGuide site with cge and cge-pro (but not cgem).
There may be more effort and care required with mid-range equipment - but the existence of results at 2" fwhm and below is proof that such results are achievable without a high end mount - and such results benefit from small pixels.
More on topic - I think it's great the OP's PE was reduced, and that may well make the mount more forgiving when guiding - but the number I like to see is the achieved fwhm in arc-seconds in long exposures - which sounds like what you are interested in also, ultimately.
Posted 28 February 2013 - 07:54 AM
For me, my iEQ45 performs very, very well. I agree with Dan: one has to know the performance of several kinds of mounts. Getting down to 4.5 arcseconds is very good. Is it for anyone else? Only each one an answer that.
The weight, cargo capacity, PEC capability and GPS were features that attracted me when I bought mine, but the main feature which made my decision was the fact that it can get to 5 deg of latitude with no other accesories required because I'm located at 4.8 deg North. So, no matter how good or bad its competitors are, they didn't work for me.
Apart from that, I have been kindly surprised by the good performance of this mount, as many other owners of it have. I know at least two other cases in which the PE with PEC has been taken to 4 and 6 arcseconds, which are in the same range as I am. Tracking is good, alignment is easy wih the built-in routine and the go-tos are always into the FOV.
Having said that, it is not a Mach 1 or a Paramount, but is a very good mount. I'm in no way related to iOptron. I'm just a satisfied costumer.
Is it the right mount for you and within your price range? You have to evaluate that.
Let us know if you need more help.
All the best,
Posted 28 February 2013 - 08:08 AM
How can the fwhm be measured? I'm very interested in measuring that.