nakbrooks

My PSU is a Siemens industrial one - not particularly cheap but seems rock solid. As an aside, how do I access the logged power data - is it logged by default or do I configure this in Autoslew?

Looks like it was a USB cable problem. The ASA cable between the DDM85 hub and the OTA had a small cut in it, exposing the shielding. When I replaced it with a Lindy cable all seems fine.

Which brand do you use Waldemar?

I was operating remotely but will try that today.

The variance identified by Mark is about 0.3% and probably due to rounding errors in the SQM Reader Pro program. I would be perfectly happy with a repeatable variance of around 0.5 mag, but can't find an easy way of calibrating my SQM/LE as there is no way of getting a "true" reading without investing in lab-quality equipment. I'll probably just have to trust the manufacturers calibration. One of the documents referenced on their website was an independent review of 9 meters, including the SQM/LE. It determined that it was impossible to identify which was the most accurate and they had a spread of around 14%, but they were all very close in terms of the relative variances in luminosity.

I've raised a support ticket with ASA for this but am posting here as well in case any other users can help. I have a problem with USB errors and “blue screen” when powering on the mount motors during Autoslew auto-find. I am using Autoslew Ver 5.1.1.6 and ACC Ver 13 on Windows 7. My USB configuration is as follows: Location 0 [uSB 3.0 Root Hub] Location 0 (Port_#0003.Hub_#0001) [uSB 2.0 Hub] Location 0 (Port_#0003.Hub_#0002) [uSB 2.0 MTT Hub] Location 0 (Port_#0001.Hub_#0003) Location 0 (Port_#0002.Hub_#0003) Location 0 (Port_#0002.Hub_#0002) [uSB Serial Converter] Location 0 [FTDI COM 6] Location 0 (Port_#0001.Hub_#0001) [FTDI USB Serial Converter] Location 0 [COM 10] Location 0 (Port_#0002.Hub_#0001) [FTDI USB Serial Converter] Location 0 [COM 5] Location 0 (Port_#0004.Hub_#0001) [FTDI USB Serial Converter] Location 0 [COM 4] My normal start-up workflow is: Turn on power to Mount. Turn on power to Mount Aux Start Autoslew Start ACC Power up mount motors from Autoslew When I power up the DDM85 motors from Autoslew the USB connection to the ASA 400mm Cassegrain (which is used by ACC to control the ASA focuser and mirror covers - the red ones above) is lost. ACC reports “Device Error” – which cannot be cleared without powering off the Aux power to the DDM85, and Microsoft device manager properties for the non-working ACC USB port show “This device is disabled because the firmware of the device did not give it the required resources. (Code 29)”. The problem occurs during the Axis 2 (DEC) Autofind process. Sometimes I get a Windows “blue screen”, not just a disabled USB. The USB cable between the Mount Hub and the 400mm Cass Hub is the one supplied by ASA. Do you have any suggestions? Is there any logging I can turn on to try and diagnose the problem? Regards Nigel Brooks

You're right that Unihedron do say that an MPSAS reading over 22.0 is "unlikely". I need to try and find a way of calibrating my meter as, although it does get very dark here, the maximum readings I am getting are s bit implausible. Not sure how to calibrate though (other than buying several other astro photometers and taking a mean - which would be expensive).

Sounds about right George. My system records data every 1 minute but I take the mean over 5 minute periods for upload to the web site to reduce data volumes so this does give some rounding.

Attached are the formulae in the Unihedron SQM user manual for converting between MPSAS and NELM. Not sure if it is these that are used in SQM Reader Pro 2 but I assume they probably are.

An MPSAS of 20.11 equates to a NELM of 5.6 (at least according to the algorithm used by Knightware in SQM Reader Pro 2). A NELM of 6.62 equates to an MPSAS of about 22.05. MPSAS is the native metric generated by the Unihedron SQM sensor, and is a luminosity measure (in magnitudes per square arc sec). NELM (naked eye limiting magnitude) is computed from MPSAS. I prefer to use NELM rather than MPSAS as I find it more meaningful (although I do record and graph both). I have attempted to independently check the accuracy of the reported NELM data by eyeballing the sky near the zenith and seeing what are the lowest mag stars I can see, but I haven't had time to do this thoroughly, and in any event my "naked eye" is probably not typical (I am 63 and wear glasses). Also of course, the SQM sensor can only measure darkness, it can't assess other aspects of seeing (such as transparency).

That's an interesting question. I can measure limiting magnitude and cloud cover objectively using the SQM and CSII sensors, but seeing is more difficult to measure objectively, particularly remotely. I've not tried it, but probably monitoring double stars of known separation would be a reasonable way of getting repeatable results. Nigel

Yes that's pretty much what I do now, I was just wondering if there is a way to set a 1-button goto or similar.

Using Autoslew (5.1.1.6) I have Park 1 set to near the Home Find position (approx vertical) and Park 2 set to where I actually park (about 25 deg elevation to reduce risk of dust and condensation from the dome dropping on to the mirror). I need a third preset absolute position for my flats light box which is mounted on the side of the dome. Is there a way to configure a third park position, or a workaround so I can easily point the OTA at the flats panel when working remotely. Thanks Nigel

The only reason to upgrade to the XL would be if you needed the extra payload. I have the XL with the ASA bent pier. I can confirm that the pier is an exceptionally solid piece of kit - probably more solid than you need for a lighter-weight payload on a standard DDM85 (as well as being expensive).

Best seeing so far this year last night at Stratis Observatory, at least according to my SQM/LE sensor. Unfortunately I wasn't there to confirm and I still need to check calibration. At least I've got the live update to the web site working (uses PHP, JavaScript, JQuery and Google Charts to display sensor info).

Can anyone recommend good Astronomy RSS feeds in German or Spanish? Thanks.

I'm not familiar with the OK3 focuser (I have an ASA Cassegrain with different Focuser), but can you see whether the focuser looks like it is at approximately the home position? If it isn't can you manually move it to home before trying ACC again? Sorry I can't help any more. Maybe someone with an OK3 can.

You say it was working before? What has changed in the systems environment? Has the PC operating system been updated, any driver changes, different ASCOM version, different virtual serial port version, different USB cables or hub, etc, etc. if possible go back to the original environment and change one thing at a time until you find the problem.

Bonjour Denis. Vous êtes en France? J'ai un DDM85XL en 65, Hautes Pyrénées. Nigel

I've had that on my DDM85XL carrying a heavy payload. Almost certainly it is a balance issue. After I carefully rebalanced (with the OTA In different attitudes) and manually retuned the problem went away. Also, difficult to tell from the video but you seem to be slewing quite fast, slowing it a bit might also help if the payload is heavy.

Anyone else have problems with snails infesting the observatory? I have dozens. I've heard copper works (they don't cross it because it sets off an electrolytic reaction). Am thinking of putting a strip of copper tape around the plinth that the dome sits on, but any other ideas welcome.

Superb shot of an ever-popular target. Wish I could do the same - I've given up attempting to collimate my new 400mm Cass as something seems seriously amiss. ASA have promised to help.

Ignore that question. Just checked the data sheet and it needs to be 124.5mm from the CCD plane, which it is.

Quick question for anyone using an ASA field flattener: Where does it fit in the image train, next to the backplate or further back towards the camera? This is for a 4" flattener on a Cassegrain OTA but I assume the principle is the same for Newtonians and smaller correctors - do they go first, last or somewhere in the middle, or doesn't it actually matter? I've installed mine next to the backplate but am having focus issues so just wanted to check. Thanks Nigel

Don't get me started on my "why don't manufacturers revert to serial connections" hobby horse!