Merlin66

Louise,

Firstly the spectrum height...

On the bench you illuminate the full slit height - 6mm hence the height of the spectral image.

When you point to your street lamp the size of the image is much smaller , hence the reduced height.

A star spectrum will only be a few pixel in height, depending on the size of the star disk at focus.

Grating rotation:

Not sure what's going on. Assuming the grating is correctly orientated, you should be able to see the zero order image as a bright single line (an image of the slit gap). When you rotate the grating one way you should find the brighter (blazed) 1st order spectrum, the blue region coming into view first ...... and when you rotate it the other way, from the zero order,  it will pick up the "-1st" order spectrum (again the blue region coming into view first) which will appear fainter.  The 1st order blazed is much brighter than the -1st order. This doesn't appear evident in your image.

I think there's no need, at this stage to flip the spectral images, it can become confusing.

The attached image shows a test shot taken with a small spectrograph.....the bright line towards the left is the zero order image of the slit and you can see to the right the beginnings of the 1st order spectrum.

Find that bright zero order line first......

Well worth re-reading Sidgwick's " Amateur Astronomers Handbook" , Section 2, Telescope Function: Resolution, p37-50.

He gives many examples of visual observations and experienced visual astronomer's experiences.

I now use the Virtual Moon Maps, but still have a paper collection.

The lpi charts shown above were available in four quadrant charts, which I still have.

Wilkins & Moore "The Moon", 1965 (use to have the Wilkins 300" moon atlas) 

Harold Hill's "A portfolio of Lunar drawings", 1991

Henry Hatfield's "Amateur Astronomers Photographic Lunar Atlas", 1968

Kopal "A new photographic atlas of the moon", 1971

Danny,

There are at least three different versions of the Meade 4000 "Super Plossl.

The original, pre 1998, was marked Japan on the black body and was a five element "Masayama clone" - seems to be the best and well worth while trialling.

The second version is marked Japan on the chrome barrel - this a four element standard plossl design - nothing special but better than some of the "Beginners" eyepieces sold with scopes.

The final version is marked "China" on the chrome barrel also a four element design and is very average.......

Hope this helps.

(I have a collection of both the black Japan (5 element) and some of the others...)

The resolution of the human eye is usually stated as 2 arc min. Fantastic eyesight (few and far between) can get down to around 1.5 arc min.

The Dawes Limit for visual observing (generally double stars) depends on the ability to discern the low contrast peaks of the star PSF maxima.

A good test is to determine the minimum magnification to resolve double stars....

I managed to resolve the Double double in Lyra at x49 (Genesis, 10.5mm TV plossl). The separation is 2.3/ 2.6 arc sec , giving 1.88 arc min for the eye resolution.

John has just released a further update to his excellent spectra processing software. Available in 32 and 64 bit versions.
Highly recommended
https://groups.io/g/BassSpectro/topic/bass_project_1_9_9_beta_3/68767134?
Changes:
Installation Folder Check

The BASS Project executable file cannot be run outside a valid installation folder. A warning message will be displayed to this effect and the app will close. The reason for this is to ensure the application has access to required files and sub-folders.  Move the executable file into the folder created when BASS was installed, (this is typically 'C:\astrobodger\BASS Project' for a default installation).

Bug Fix: This is a fix to the 'BITPIX must be second keyword' issue which applied to profiles created in the Resampling screen

FITS header: Keyword BAS_MEX for BASS Project Universal Mid-exp Date added

File menu: Maximum number of recent profiles and projects increased from 15 to 25

Chart settings: Can be edited when no profiles are loaded.

Profile Properties: File Rename message makes it clearer that a new filename must exclude path.

Region Selection tool: now includes a Cross sectional plot. This is already documented in the latest user guide

Cosmic Hot & Cold pixels screen – Now supports bad row and bad columns in Cosmetic file. In addition, bad pixels can be manually set by double clicking on the image (without needing to be detected).

Stack Images screen: Cosmetic file is applied to all light, dark, flat, bias and flatdark images.

Well done Andrew, very impressive!

Louise,

The slant of the lines in your spectrum isn't a show stopper. BASS can easily correct for this  - see the example I posted, it had slant corrected.

What is probably more important at the moment is rotating the grating >>>through zero image >>>> to the 1st order spectrum.

Ken

Louise,

As I mentioned earlier this , I think this the "-1st" order...

The bright section is the red emission in the CFL, and should appear at the right side of the spectral image. The zero order is well over (out of frame) towards the righthand side of your spectral image as presented above.

Adjust the micrometer to move towards the right of the above .....note the zero order reading - then keep going until you find the spectrum.

Relax, you'll soon be there....

(The tilt of the spectrum across the FOV is the camera tilt.... the slant of the lines within the spectrum is the slit/ grating alignment)

Thinking about it.....

I think your seeing the - 1st order (minus 1st order).... as you move the micrometer clockwise you're moving down towards the blue....you should keep this clockwise adjustment going further and you'll find the zero order, keep going and you'll eventually find the blue region of the 1st blazed order come into view.

As you increase the micrometer reading you should be moving towards the red end of the spectrum.

Yes, the spectrum generally looks good, it will be even better when you find the 1st order.

You're almost there......

No ghosts in the machine!!!

Louise,

Looks like there's an issue with your grating rotation.

Image #4 shows the typical flouro spectrum but reversed...

You need to either flip the images or rotate the camera by 180 deg to get blue to the left of the spectral image.

When flipped and slant corrected it calibrates nicely

Louise,

Hmm I was assuming the slit plate was similar to the original Custom design they produced for me... do the numbers show correctly from the front - in the guide camera?

The zero order will be further to the left - micrometer anti-clockwise rotation.

As Andrew says check the grating grooves align with the slit gap.

Ken

I'll repeat my recommendation:

Before using any threaded adaptor, give the threads a slight smear of boot polish - your choice of colour

This will significant reduce the possibility of the adaptor locking up. No out gassing or liquids to affect optics.

19 minutes ago, Thalestris24 said:

reverse numerals is also very shiny

Louise,

When viewed from the front i.e. the telescope side these numerals will appear normal. Sounds like it's in the wrong way.....

Ken

Louise,

OK...

Looks like you were observing the 2nd order spectrum! The dispersion, using your two lasers are reference gives 1.49 A/pixel rather than the 1st order 2.88 A/pixel.

This could account for the ghosting - these could be fainter lines out in the 1st order red showing into the 2nd order.

You need to re-set the micrometer to rotate the grating back to find the bright zero order of the slit, then just a small adjustment to bring the brighter 1st order spectrum into view.

Ken

Louise,

Thinking about the ghosting...it could be typical of internal reflections within the glass slit plate. These are normally seen by the guide imager rather than in the spectral image.

Could you double check the slit plate is correctly installed with the reflective surface sitting towards the collimating lens

https://commons.wikimedia.org/wiki/File:Fluorescent_lighting_spectrum_peaks_labelled.gif

Shows a Hg line around 4046.6 A.....

Working on it...

Louise,

Don't bother!

I found the answer was to open the image (in SGL) then save.

It is full size!

I assume the laser matches...

Ken

Louise,

PM sent with details

ken

Louise,

The image is still coming out at 1200 pixel wide....

The tilt of the laser line image looks odd - the tilt should mirror that of the spectral lines.

To use the laser as a calibration point it must be taken with exactly the same set-up as the target - same camera, same micrometer setting. Unfortunately the references I have for fluoro lamps don't go down to 4050 A, but I'm pretty sure there are no bright lines down there - your target spectrum (if matched) shows a double line close to this wavelength???

Can you email me a raw full sized ( 3354 pixel width) copy of both images?

Ken

Ok.

The first bright line you should find moving from the zero image is the blue line of Mercury at 4358 A.

Make a note of the micrometer reading for the zero image and any subsequent bright lines - this will help you to find and identify them in the future.

Try an exposure which maximises the red without saturation.

Ken

Louise,

Well done!

Promising start. I agree with your SimSpec results. A couple of things: Place a diffuser over the inlet port (piece of white paper) this may help suppress the ghosting.... your 8 sec exposure is a bit too much, the red end is saturating.

Also try again with the grating reversed, ie turned upside down just to make sure you're working with the first order - it should be the brightest spectrum.

Dropped your .jpg into BASS - the image is only 1200 pixel wide whereas the ATiK 383 is 3354 pixel complicates the calibration...

I'm unable at this stage to find the lines I need.....

Louise,

Well done!

I must say I'm a little surprised that your "DIY grating" is giving you a result.....

At this stage you're ready to go for the real grating.....

Using a narrower slit will give you better resolution, try 20 or 30 micron.

The Simspec spreadsheet should allow you to determine the wavelength coverage.

Onwards and definitely upwards.

Vlaiv,

Yes, that's it.

An easy and handy way of measuring Barlows.