Merlin66

"2B or not 2B....that is the question.."

Louise,

Right click on the image (active image has the yellow boarder), Profile Properties/ Line/ Line colour and select the colour you want....repeat for the other profile.

Yes, you can crop the X axis - Chart/ Crop X axis range.... selected the wavelength coverage which suits, then revert by Chart/ Uncrop X axis.

To get a reasonable calibration you only need to identify say 5-6 (max) lines across the spectral image - set Calibration fit to Quadratic.........

Ken

Eric,

Re-reading your post...

What were/ are your issues with the reflective slit acquisition and guiding? Do you have a guide image to share?

Many of us now use the OVIO slitplate for guiding with few if any issues. Why do you think the illuminator is worthwhile fitting?

What slit gap did you use?

Eric,

Well done mate!

Looks like you're of to a good start.

I have a pre 2009 Pentax zoom - said to be a SMC XW 8-24 mm zoom , nitrogen filled.

I use it for solar observing - no issues.

I realise you have the S10 data. But calibrating say the Fuoro then using it as a BASS reference (or visversa the S10 calibrated to the data given used to re-calibrate the Fluoro) gets you closer to the final real world processing of a reference and a target start spectrum.

Louise,

Looking promising....

You could use your FCL as a "reference" image to provide the calibration for the S10 spectrum....

This would get you into the ball park..you can then refine the calibration using identified lines.

No rush, no pressure...

identify the line from the fluoro profile I posted and read the wavelength from the same fluoro profile, enter that in the calibration pop up screen.

When calibrated, this image then becomes your “reference image”

when you take a Spectral image of a star, you will also take an image of your reference lamp ( fluoro, Neon etc) then use that image to calibrate your star spectrum, the “target spectrum”

I’ll let you have a good nights sleep......

Louise,

I recopied the fluoro reference I use to my last message..

Just select the line, look up the wavelength (from the reference image I gave) and enter that, continue for the lines you can see.

We're not trying to really identify the lines at this stage, just use them to provide a calibration for our system.

Some good tutorials here: https://groups.io/g/BassSpectro/wiki/Tutorials-%26-Guides

Louise,

Well done! I see you using BASS Project....

Use the earlier fluoro reference, it's more reliable. Put it down to different CFL lamps.

You could also image a solar spectrum by pointing the LowSpec to a bright sky...

The profile you show is very promising, you'll get a better result using multi-point calibration..

The scaling of your result ----not quite correct. I think you may have used a setting which would apply to a target spectrum, not a reference spectrum.

I would also change the wavelength units to Angstroms...more widely used in astronomy.

Brendan,

Forget the cables which came with the mount.

If you want a direct connection between your computer and the mount you need a special EQDir cable.

You also need to install ASCOM, then EQMod and an interface planetarium program, I use Cartes du Ciel.

Once set up you have total remote control of your mount......

Start with the fluoro and the neon......

relax and spend some time playing with BASS Project.

http://www.astrosurf.com/buil/calibration/lamp1.htm

The Filly lamps were decorative lamps sold a few years ago. Buil did a review and they proved to be popular. Yes, the spectral data for the FILLY lamps is available.

ProAm is a collaboration between the proffesionals and amateur "data collectors"

Louise,

On the Astronomical Spectroscopy IO group there's some info (I think in the files area) on alternative Relco type lamps. The Telluric absorption lines/ bands make a good double check.

I use the Habitat FILLY decorative lamps - "Blue Cross" for calibration in short wavelengths (unfortunately now unavailable) , and Neon in the Red.

Most of the ProAm requests are for specific wavelengths, so calibration is important.

Ken

Hmmmmm

Many older objectives were cemented together with Canadian Balsam......

https://en.wikipedia.org/wiki/Canada_balsam

I’ll contact Paul....

yes, a reference lamp ( neon or Richard Walker’s fluoro starter bulb) is mandatory for successful slit spectroscopy.

Ken

I don't have any first hand knowledge of the LowSpec, so I have to assume that Paul designed it correctly.

In my Littrow, with an 1800 l/mm grating which gives a limited wavelength coverage, I have to refocus at every micro setting.....the focus can vary up to 1.8mm across the visible spectrum.

It was 42 deg C yesterday and they're saying tomorrow could be even hotter!!!

Louise,

No disrespect intended...I just wanted to reinforce the relative positions of the first order spectra to the zero order image.

OK. Looks like you have managed to get the zero order! 

Your second image above looks like it covers the main Fluoro spectrum from blue to red and should compare favourably with the earlier profile I posted.

From the micrometer settings you quote ie Zero at 176 and the centre of the first order at  411  it seems in the LowSpec design that the grating holder rotates in the opposite direction to the Littrow spectrographs I have. For me the zero order is found at a much higher micro reading (I use a 25mm micro) say around 1500 and depending on the grating used can go down to 1050 to centre the red line of the fluoro lamp.

Obviously if the zero is at only 176 there's no chance of going further to pick up the first order on the other side of the zero order.....

With a slit spectrograph, other than during initial set-up ( as we're doing now), you will probably never look at or use the zero order again. Once you have the micro settings for the various wavelengths ( I centre Fluoro Blue (FB), Fluoro Green (FG), Fluoro Yellow (FY) and Fluoro Red (FR)) to give me a quick calibration guide...ie

Zero 1540

FB 1277

FG 1100

FY 1072

FR 1049

Using these settings allows me to quickly set the grating to the wavelength of interest. When you commission your reference lamp you can refine this calibration.

Now you're up and running..

Rotate the camera 180 deg (if you can) to bring the blue region to the left hand side.

Practise different focus positions to find the best result - at the moment I think your blue focus is tighter than the red. Depending on the quality of your optics and the set-up accuracy of your Collimator/ grating/ imaging lens, you'll find this is a compromise.

At this stage I would be looking at BASS Project to help analyse the spectra you're recording. Another learning curve - but there are a few good tutorials available to help.

Well done!!!

Ken

John,

Interesting...

The Meade 4000 "black body Japan" eyepieces I have, from 6.4 to 32 mm all show neat tight field stops.

I'm not saying they are the greatest eyepieces I have in the box, but certainly seem very capable. Better than the Chinese Series 3000 I have.

This may help....

Louise,

Check out the illustration on ASA, p42.

It shows the relationship between the various spectral orders and the zero image.....may help your understanding.

Louise,

OK.

It could be your starting point for the clockwise rotation was already too far from the zero position.

Unwind the micrometer almost completely, then slowly go CW watching what happens - you'll probably find a spectrum....keep going....dark space....then hopefully a zero order line image ....note the micrometer reading....keep going.... dark space.... and you'll find another spectrum. Hopefully the second one you find will be much brighter than the first. This is the one you want.

Once you've got zero image/ spectrum you're in business.

Ken

The 2nd and subsequent spectra are always fainter the the 1st order due to the increase in dispersion.

Louise,

It's Wednesday down here in Oz.....

The reason initially for flipping the spectrum was due to your sequence of images 1-7 this appeared to show that you were moving towards the blue as you increased the micrometer, rather than towards the red.

(If you had continued this sequence ...... you probably would have found the zero order)

If you can get the micrometer to the zero image then you can confidently determine which order of spectra you're observing  - a faint one on one side (-1st order) and a brighter one on the other side (blazed 1st order)

Generally by winding the micrometer inwards ( lower value on the micrometer dial) from the zero image, you hit the blue side of the spectrum first, then onwards to the red.

I think you had the grating position well away from the "normal" operating range and came into a spectrum from the "other side" ie red end first.

Hope this makes some sense.

Ken

Louise,

Don't flip the images.

Look at your previous CFL images....the fainter lines are towards to blue and the brighter, wider, hazy line is at the red end. This should give you some guidance as to which part of the spectrum you're imaging.

The zero order is a defined bright line.....

When you look at your spectrum of the CFL, the distance from the first line to the red haze is about the same as the distance from the blue line back towards the zero order. ie if your CFL spectrum fills about 2/3 the full CCD frame then the zero order will be found  around 1 to 1.5 (approx) FOV from the blue line.

Don't worry about the blaze angle...(check p 148 > for technical details - not necessary to know at this stage)

Hope your ecg app goes well tomorrow.

Ken