SteveBz

It's arrived. I'm about to start printing. I'll have to run some tests, but it might save some time if you can tell me whet temperature(s) and resolution you used on your printer. Tx. Steve.

Doing the main body in the 'GreenTec Carbon', but to fill in time until its arrival I'm building non-critacal parts in this rather strange blue PLA. Can I do multiple parts like this?

Doing a test run of the autoguide tube. First one was very wrong, but looking OK so far...

Done. On order. Thanks guys.

Guys, Are ABA and ABS the same thing? It would appear so. Kind regards Steve.

Great I only want to print the LowSpec 3.0, and maybe the Sol'Ex/Star'Ex from AstroSurf, if I'm successful. It says it can handle Carbon Fibre ABA, so it looks OK. Youtube says I have to upgrade the nozzle to stainless steel because of the temperature, and I'm also buying a heated filament dryer. Tx Steve.

I want to do a survey of galaxy rotation curves for a variety of local galaxies. Maybe use the Maksutov to build and test the Lowspec 3.0 and then when I have it working, I can upgrade the scope (there's a question here of cashflow 😄). My current, cheap, 3D printer seems to be malfunctioning. I was thinking of buying an Ender 3 to do the job. Is this an acceptable quality printer? It seems almost too cheap to be real. Do you have a recommendation? Kind regards Steve.

Hi Paul, I'm thinking about building the lowspec 3.0. I have a small, light Matsukov, about f/14. Is that too slow, do you think? You talk about f/10 a lot, so my question is do I need to invest in an f/10 scope, like an RC or an SCT? Kind regards Steve.

Then I can use it with the f/4.4, small, light-weight Newtonian (It's a small Bresser 114 mm x 500 mm) and not worry about the Meade ETX90. It doesn't seem very difference in price. Both about 2k for the full kit.

This one of M77 is what I imagined it would look like, but with an ALPY? It says T200, is that the same as the ALPY 200 grating that you talk about? I can't even imagine it has that resolution! But this one, with an ALPY 600 (no doubt this time) it's tilted the slit along the axis of the galaxy. A much better idea. So either way Alpy cuts it here, it doen't need an LHIRES III, or even a DADOS, as I was suggesting in the other thread. Good point. So basically, if I save up for an ALPY 600, it's good enough to produce one of these curves, is that right? Great. Kind regards. Steve

Hi Guys, Do you know where I can find spectra of edge-on galaxies (or highly inclined galaxies) with regular spectra taken along the galactic axis that I can use to calculate galactic rotation curves? Thanks Steve.

I agree about the 'Sanely-priced' point. In fact even with the APLY 600, clocking in at about £2k with the calibration and guiding modules. If you don't want to tear down your main rig, you have to allow another £1,000 for new cameras and stuff. I bought a side-by-side bar and mounted a small Newtonian on it sharing the EQ6 that seemed to work, but I only have an SA100, and like you I want to move to a slit-based system. My SA100 + f/5 system has R<200. The ALPY 600 is, um, 600 I believe, but I'd like something more like R = 5-10k. So I was thinking of the Baader Dados which also weighs in at about £2k. The advantage is that it doesn't absolutely require a guide-cam as it comes with a guiding eyepiece. I can imagine that might become a bit tiring quite quickly, but it would be a start. I also have a small Meade ETX90 and I wondered if I could use this with the Dados. It has quite a long focal length so it's f/13.8 I think. The Dados seems to be designed for an f-number of greater than f/10, so I wondered if this would be a good solution. What do people think? Kind regards, Steve.

Wow Victor, I didnt know. Do you think my 1.3 m dish is big enough to get the Crab Nebula, for instance. It would probably gave to be a bit more steerable than it is. Kind regards, Steve.

I feel I've got as far as I can go here. I've suppressed some of the worst invalid numbers. So here is my plot with its asymptote at 180 degrees (I don't know what I can really do about that) compared with the same plot for LAB values on the right. Now I think I'll spend some time thinking about rotation curves. Thanks for reading this far and thanks @Victor Boesen and @ZiHao for your support and help. Kind regards Steve.

So my Python is definitely not working. Here it is based on the LAB survey: Some looks right and some looks crazy. Steve.

Hi ZiHao, I think I've found one error. It was the r = r +/- delta_r bit and obviously for QII & QIII there is only one solution which is the r = r + delta_r one. I still have quite a lot of further non-standard points. Here's a cleaned up version: I'm tempted to download the LAB stuff and see what happens if I chart that. Thanks for your help. Steve.

I don't use @Victor Boesen's corrections yet. These are the ones we discussed a few pages ago. These are just the raw frequencies, uncorrected.

And what do you get for R, X & Y?

Yes it's here. Thanks for looking. Steve. debug(ra=94.1,dec=21.1).json

I think I said the labels were the quadrants, yes? So the 1's look right. Some of the 2's look right. You can see that's it's gone asymptotic at 180 degrees for somew of the 2's and all the 3's. There are two 3's south of the GC. These have angles very near 180. Then there are a load of 2's in quadrant 4. I don't know what is happening there.

Actually 6 or 11, makes little differnce. They both come out R<0. I must have got the formula wrong.

Hi ZiHao, I think you're right, it is the LSR. However, I can't see how it's wrong. Here's a plot: My values are in the red box. rv = 11 km/s and R is negative. Obviously that is not going to work out well. l = 190 deg is quadrant 3 and should have positive X and negative Y. The opposite is true. The corrected LAB value is 6 km/s. The LSR and planetary compound correction value is -41 km/s, quite large in comparison. The orange curve is the Gaussian-fitted curve. If anything it's skewed to lower values. I started by calculating the corrections independently (-29 km/s and -12 km/s) and then togther by feeding the planetary correction onto the LSR calculation. Both give -41 km/s. Noty sure what to do next. Steve.

It's possible, isn't it. I'll look at that. Tx.

Here I've replaced the marker with the quadrant number for debugging purposes. You can see that some of it fine and some is very strange.

My numbers near 180 on both sides are very strange! Sometimes R is positive and sometimes negative, which doesn't really work. 😅