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All Activity

1. Past hour
2. QHY163c - Strange ADU behaviour. Bias & Darks Median ADU are double the expected amount (Offset)

I'll examine subs you posted, but there could be a simple explanation. I can't remember now, but it was discussed sometime ago - offset can be added at both pre amp and post amp stage - meaning that it can be multiplied by gain or not. This could be one explanation. Second explanation would be that since some vendors use gain in arbitrary units, offset might also be in arbitrary units? I remember older QHY cams having 0-100 gain in some drivers. That did not translate into anything meaningful, or one needed to measure e/ADU values to get proper correspondence. Is there a "table" or formula for gain - e/ADU conversion for this camera? Maybe offset is implemented in drivers in similar way - meaning 0-100% of possible offset ranges (which are real numbers but something like 0-220e or something like that).
3. Relays for Lesvedome

Treat the battery negative terminal and everything connected to it as Ground or 0 Volts. I assume all the equipment is fixed to the rotating roof so as you say there is no actual physical. connection to the earth for a true Ground connection. Ground in your instance is just a nominated point which you can call zero volts to which all the other voltages are referenced to. As your system has no physical ground connection you can't make any voltage measurements with your multimeter if you connect your black meter lead to a true ground like you will have in your home. So you have to nominate one voltage in your system to act as a ground for making measurements. The most logical is the battery negative terminal. Talking in terms of 12V+ and 12V- could imply +12V and -12V which have 24 volts between then. Calling the 12V- terminal 0V or Ground for convenience, removes any ambiguity in labeling. As your system is only 12V powered you don't need a physical ground or earth connection for safety reasons like you would with mains voltages. Alan
4. Where does idea of infinite size of universe come from?

Point being? Density in this case is - take any interval within 0-1 range, 0.3-0.4 for example and divide length of that interval with count of numbers within that interval or 0.1 / ∞ ~ 0 (any finite number divided by infinity is infinitesimal). This statement is not correct, and again one has to be careful when working with infinities. Basic division or types of infinities are countable infinity and uncountable infinity. Interesting fact about rational numbers is that there is countable infinite number of them - same as integers - this means that there is "the same number" of rational numbers and integers. Have a look here: https://www.homeschoolmath.net/teaching/rational-numbers-countable.php Page already emphasizes important sentence, and I'll just copy it here: "a set is countable either if it s finite, or it is infinite and you can find a one-to-one correspondence between the elements of the set and the set of natural numbers" Finding one to one correspondence between two sets in fact means they contain same number of elements (as for each element in one set there is exactly one corresponding element). Real numbers on the other hand are uncountable - meaning there is vastly more real numbers than both integer numbers and rational numbers - again point given above, difference being all irrational numbers.

Dave - just to say I ordered and have received the dual channel dew heater control as per your suggestion at: /www.dewcontrol.com/Dual_Channel_Digital_Dew_Controller/p3099125_13437758.aspx It looks well made, and arrived quickly. Looks just the job - thanks. Annie
6. Sharpcap PA and Lodestar X2

I'm planning to use Sharpcap for Polar alignment, which gets good reviews, using a Starlight Express Lodestar X2 mono guide camera, combined with a William Optics 200mm FL x 50mm guide scope, which I calculate provides a FOV of 1.85 x 1.38 degrees. I've been using this set-up successfully with PHD2 for sometime. Given the above parameters + before proceeding further with Sharpcap I wanted to confirm: 1. Will the pixel size of 8.6 x 8.3 nm, which is not square, work OK with Sharpcap and plate solving, which I understand is an integral part of the polar alignment routine? 2. Will the installed ASCOM driver for this camera used with PHD2 be OK with Sharpcap or do I need something else - if so which one? Thanks, Graham
7. Where does idea of infinite size of universe come from?

We have to be aware of infinities and there place in the real world...to take an example highlighted upon before and look at it differently. There are obviously more non-integer numbers than integers.... I think this makes sense. In fact there are infinitely more non integers than integers.... again look at 1 & 2 and count the non-integers between them ( might take a while ). Statistically Integers do not exist ! It can have weird effects when you move from reality to imagination. It would seem to make sense that infinities do not exist in the real world, ie nothing you can observe can be infinite. ( or be part of anything infinite ).
8. Bresser MC-127 Maksutov Collimation Adjusters

@Paz Hello, did you figure collimation out ?
9. Struggling to get a decent image of Jupiter

this is mybest effort of jupiter with a little mak 90 and an asi290mc
10. Where does idea of infinite size of universe come from?

Isn't density a ratio.... and hence by definition....rational ?
11. The "No EQ" DSO Challenge!

I never thought about the possibility that too few darks can add noise... I have to make sure to remember that darkframes are just as important as lightframes haha. What exactly is binning? I may be confusing it with drizzle. Also, if a gradient is barely noticable, are flats really needed? I tend to crop images more and more, except for targets that are too big for my FOV like M31.
12. The "No EQ" DSO Challenge!

That's a great set, I particularly like m57. I have found 100+ lights with 30 flats, 30 dark flats and bias makes a difference and if do use flats then it is 30 again. Too few darks I find adds noise. There is a point of diminishing returns but me me that is controlled more by how long I will stay outside or whether the object is moving out of view. For uploading as I bin my images they are always nice and small file size so are around 3 MB each only.

PM sent
14. Bank holiday todmorden pier

Thanks for that. They look very useful. James

16. Recent moon

Finally waded through the AVI's taken a week or so ago. One image with a C6 and the other with a C9.25. I like the ridges near the straight wall.
17. Today
18. Longcase Pendulum Clock

The centre wheel and the intermediate wheel were both at fault and I'm reprinting both.
19. Cygnus widefield 20 panel mosaic HA

Stunning image.....
20. Relays for Lesvedome

Alan Thanks for that explanation and for doing more drawing for me. I have clearly not drawn the DPDT switches correctly nor explained them. The two I have are actually 3 position with the central one having no continuity. That's what I meant by "off". I suppose that the motor switch could have been a more basic two position switch as with the main switch at off there is no power flow anyway. On the connections to battery's 12V- this comes back to my problems of interpreting some of the example diagrams accessed via Lesvedome e.g. https://github.com/tonygilkerson/astrobagel/wiki/Observatory-Automation-with-LesveDomeNet and http://eplumer.blogspot.com/2010/01/observatory-gets-automated-dome.html which show more direct contacts with 12V- than just ground. What I need to do I think is trace them all in my head to see that they are essentially all just ground connections. Physically however what is that connection, if it's not to the battery's 12V-? In buildings there are ground straps to earth but the rotating part of the dome is essentially insulated from earth by the plastic rollers on which it moves and the rubber tyres on the motor drive roller and guide roller which are in contact with the non-rotating walls. So even the metal housing of the Pulsar/Rigel system is not a true ground. Thanks Peter
21. The "No EQ" DSO Challenge!

Here i am again, now with a Nexstar 102SLT on the stock AltAz goto mount. It is actually easily possible to shoot DSO's with an AltAz goto Mount, not even remotely as hard as EQ users tell you. Here are my efforts from just 1 single night, around 3 hours of being outside and aligning the mount, focusing, testing settings and searching for targets. All frames were taken 05.22,2019 night, through 05.23.2019 morning. All of the following Pictures were shot with a Nexstar 102SLT on the stock AltAz Goto Mount with a stock Nikon D3400 at prime focus, no extensions tubes, filters, coolers, heaters, field flatteners or anything else. Messier 81 and Messier 82, Bode's Galaxy and Cigar Galaxy. 49x15" ISO6400 15 darkframes Messier 57, the Ring Nebula 10x13" ISO6400 9 darkframes i forgot to defringe in Photoshop... But i got the central star in the Nebula which is a plus NGC 6992, a bit of the (Eastern?) Veil Nebula 28x13" ISO3200 (shouldve used 6400 here) 9 darkframes (this was the last DSO and the camera battery was dead) couldnt defringe because i would lose the Nebula's color. Messier 51, the Whirlpool Galaxy 28x10" ISO6400 9 darkframes every EQ user ive seen said/wrote that anything within 30° of zenith is impossible with an AltAz mount, which isnt true at all. In my location at this time of the year, Messier 51 is almost 82° high. No matter what EQ Users tell you, Astrophotography is very much possible and fun with AltAz mounts. Messier 13, the great Cluster in Hercules. i deleted the RAW files and cant remember the settings, but it was ISO1600. i cant get rid of the gradient because i didnt do any flatframes AND the Moon (can you believe how much i hate this Moon guy :P?) was 99.81%. Anyways, this was the first DSO i shot with the Nexstar 102SLT. Messier 27, the Dumbbell Nebula 18x13" ISO3200 9 darkframes Everything was processed in DeepSkyStacker, Photoshop and Lightroom. Very basic processing, Deepskystacker: Stacking ofc. Photoshop: histogram strecht, color correction, LP removal, contrast. Lightroom: noise reduction and final WB correction. I had to crop the images because they were over the maximum filesize that Stargazerslounge allows. Huge because the D3400 shoots in 6000x4000 and Deepskytacker loves huge files. I still got questions tho. If i take more lightframes and darkframes for, lets say M81 and M82, and stack upwards of 200, will the SNR improve by a lot? it seems to me that stacking 20-150 frames will reduce noise by a lot, but anything over that doesnt do anything. Is there a limit at which the SNR cant improve anymore? Criticism is very welcome!
22. What did the postman bring?

Postman delivered my Giant alt-az mount today. Thanks Zoltan! 1st inspection looks good!
23. Struggling to get a decent image of Jupiter

Hi Paul, I'm not familiar with SharpCap as I use FireCapture, but can you select a smaller region of interest (ROI), as you have a lot of black sky above and below Jupiter? The black sky adds nothing to the image, (unless you are trying to capture distant moons to the left and/or right of the planet), but it's all data that has to be downloaded, so it really slows down the capture rate. If you can set an ROI around Jupiter or Saturn, then you should see a significant increase in the fps. If SharpCap doesn't allow setting an ROI then I would encourage you to try FireCapture, which is what many of the top planetary imagers (Damian Peach, Christopher Go, Anthony Wesley, Avani Soares, etc.) use. It is free software, so definitely worth taking a look at it. (http://www.firecapture.de/) Also you can improve the Jupiter moon image by processing that seperately to align the RGB channels and then accurately placing it back over the main image, typically approximately where the green channel moon image is located. That said, I think they are both a pretty good images and I envy your Qld, Aus location with the planets running high in the sky. Keep them coming, there's a lot of interesting developments in the GRS right now, so definitely worth capturing images to monitor that. Good luck, Geof
24. SGL 2019 SP - Bookings Open!

I'd like a spectroscopy session if possible
25. Scope Handles... 'Andles for Scopes! :D

Yes same one on the Tecnosky version of the Altair 152mm. PS: you need matching spaced holes in the dovetail. Dave
26. Bank holiday todmorden pier

Do you have link for the anchors in the top concrete block for fixing the pier adapter? I have another job where that sort of thing might come in quite handy. James
27. A Year of Observing

Nice work Bob. I record the number of the sessions in the year. (Currently at no. 41 - not so bad.) And I also keep tabs on exactly what I've seen, but in simple, written records! Doug.
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