SteveBz

On 27/06/2022 at 12:24, Paul Gerlach said:

Green Tec Carbon from Extrudr

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...

On 27/06/2022 at 12:24, Paul Gerlach said:

Green Tec Carbon from Extrudr

Done.  On order.  Thanks guys.

7 hours ago, saac said:

Steve,  I bought the Ender 5 a few years back;  Paul's LowSpec spectroscope was one of my first serious print runs with it and it performed really well. The Ender 5 and 3 are very similar save for a different frame design so I think you will be pleased with the Ender 3 if you go for it; build quality is certainly very good.  I've only ever used PLA with mine so I 'll follow with interest if you use Carbon Fibre ABA to see how you get on. 

Jim 

Guys,

Are ABA and ABS the same thing?  It would appear so.

Kind regards

Steve.

2 hours ago, Paul Gerlach said:

The Ender 3 is a cheap but capable printer. If you only print ones in a while than this is a perfect printer.
 

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. 

2 hours ago, Paul Gerlach said:

Hi Steve,

It's been a while sice I've been here. Only now saw your post.

A maksutov is a great telescope for planet  photography but not so for spectroscopy. The Lowspec 3.0 will work at f/14. It's just not optimal. So if you want to start with spectroscopy, then by all means, use it.
As you become more experienced and want to do some serious observations, then you can always progress to a better suited telescope.

 

Best regards,

Paul

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.

On 04/01/2020 at 13:49, Paul Gerlach said:

Nice results! I'm a bit surprised though that he uses a f/4 newton. When using the 1800 l/mm grating and use anything faster than f/10 you will lose a lot of light that is just not falling on the grating. Even at f/10 you will lose some light with a 25 x 25 mm grating (width of the light bundle falling on to the grating is (according to SIMSPEC) 26.8 mm. That's why I advice to use a 30 x 30 mm grating in the new assembly manual.

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.

Just now, SteveBz said:

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

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.

39 minutes ago, robin_astro said:

https://www.spectro-aras.com/forum/viewtopic.php?f=6&t=2618

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! 

40 minutes ago, robin_astro said:

http://www.spectro-aras.com/forum/viewtopic.php?f=6&t=1682

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.

28 minutes ago, robin_astro said:

For exactly edge on galaxies the conversion to a rotation curve  is not  straightforward though as at any given location, the spectrum is potentially a combination of regions at different radii, each seen with a different component velocity in our direction. 

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.

On 07/04/2022 at 21:08, riklaunim said:

Anyone here used Alpy 600 or something similar? I'm looking into slit based spectroscopes and I don't see much options (sanely priced). I used Star Analyser before and now I want something with a slit to target nebulae but also planets, like specific features in Jupiter atmosphere or like sodium emission around Io and so on (and comets if they show up).

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.   

On 05/05/2021 at 18:27, Victor Boesen said:

Not to mention pulsars as well! Definitely something I want to try at some point.

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.

2 hours ago, ZiHao said:

Alright, I tried plotting the results just now and I have the same results, rv=11. This is interesting, are your rv for spectrum of other locations off by few kilometers as well? If yes, then I think it will be good to check with @Victor Boesen LSR correction and compare the results.

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.

2 hours ago, ZiHao said:

Alright, I tried plotting the results just now and I have the same results, rv=11. This is interesting, are your rv for spectrum of other locations off by few kilometers as well? If yes, then I think it will be good to check with @Victor Boesen LSR correction and compare the results.

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

5 hours ago, ZiHao said:

I think there's some mistake with the formula that you are using, I tried plugging in rv=6.18, as well as rv=11, I get positive R. You can refer to the notes I attached earlier or the equation you corrected in the pdf. Is it possible for you to send the raw data for this spectrum, l=190? I will try to correct it to LSR later and see if it matches with LAB survey.

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.

34 minutes ago, SteveBz said:

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.

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

On 25/04/2022 at 15:07, SteveBz said:

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

Tx.

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.

3 minutes ago, ZiHao said:

Hmm...Are the LSR corrections correct? I try substituting the values from the LAB survey, they seems to give positive R. If the corrections are correct, then I guess you have to reject the values obtained near l=180, from the earlier pdf paper you shared, it seems like there is no data points around that area also.

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.

2 minutes ago, ZiHao said:

I don't think you should worry about the sign in this case. If you want to substitute V=-V0 into the equation(the one that differs with a negative sign) for Q3 and Q4, we will still get the same equation. You can also try playing with the signs in the radial velocity formula and the patterns of receding, approaching, etc in the quadrants will match with what we expected.

At locations for l=0,90,180,270, I believe there will be a peak centered more or less at 0km/s because the velocity of component is parallel or perpendicular to us so radial velocity is zero. The R at l=0,180 is not easy to obtain with this method. I am not sure about what are the other methods to obtain the particular R at those locations, but perhaps the other peaks around the 0km/s peak should give a good enough indication of the vicinity of the region that you are observing.

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