Merlin66

Vlaiv,

It works 100% for every negative lens - like the Barlow.

I have the sketch somewhere...it's just thin lens formula/ theory.

You can get reflections from the front and rear glass surfaces, these would be suppressed with good coatings.

It’s very easy to measure the focal length of a Barlow.

Draw a circle on a piece of card twice the diameter of the Barlow lens, focus the sun’s image on the piece of card - when the image fills the circle, the distance between the card and the lens of the Barlow is the focal of the Barlow.

Condensation drips???

Kev,

I think you're probably at the limit of the accuracy of the mount, the temperature  variations, ground movement, and all the other influences.

Louise,

Yes, the collimator images the slit gap and presents parallel light to the grating.

The camera lens, when focused for infinity, should then show an image of the slit gap in sharp focus.

By design, I think in the LowSpec, has the collimator lens holder positioned to suit the recommended lens focal length and the design slit position.

I don't know enough about the final design to recommend how the collimator lens can be adjusted......

Louise,

A halogen lamp doesn't show any spectral detail - that's why they are commonly used to prepare imaging flats.

The back focus of the lens would be measured from rear surface of the lens (not 100% correct, but near enough)

Ken

Louise,

I think the top section is probably a reflection from something...wait until you use the proper grating.

Ideally, the spectral image should be centred across the camera chip, looks close. Improve the focus and you should get close to a recognisable spectrum with a fluoro lamp.

Louise,

Seriously, get the testing completed on the bench with a fluoro lamp before worrying about star testing.

Much easier, repeatable and satisfying.

Jim,

The separate lenses of the doublets..... you'll need to space them. Three small strips of sellotape equally spaced around the circumference would work.

The SimSpec spreadsheet with give you a good approximation of wavelength coverage with your camera, as well as the resolution.

SimSpec V4.3_Paul3D.xls

Looking promising.....

Almost there.

Hmmmm,

I thought it was the other way round.

They were going to ban the old incandescent lamps and replace them with the low energy fluoro lamps......

That was back in 2007.

Ken

Louise,

Under the circumstances you're doing well......

You'll be reinvigorated when you see that first Fluoro spectrum appear!!!

Ken

Louise,

Any progress???

Louise/ Rocky,

Yes it's a 100% easier to do the initial testing on the bench with a Fluoro Lamp. 

The attached profile shows the typical Fluoro spectrum. (From Buil's website)

Rocky,

Don’t panic!

1. The focus on the slit plate looks promising. Narrow the slit width for the final tests.

2. Use a Fluoro lamp to illuminate the slit gap.

3. Re- Focus the imaging camera to give the narrowest slit image ( check the FWHM)

4. Use the micrometer to view the extent of the Spectral image. You should see, moving from zero order, the blue flouro line, the green line, then the yellow double and onto the red.  

You’re getting very close.

ken

+ 1  for FireCapture.

Works for all my ASI cameras.

They also have a support forum:

https://groups.io/g/firecapture

Louise,

Yeah, that's what I use....

You can also get hand held portable version.

https://www.ebay.com.au/itm/12V-Fluoro-Work-Light-Accessories/163334673770

I'd recommend starting the "testing" on the bench with a fluoro lamp illuminating the slit.

Louise,

Looking good....

I think the time has come to re-assemble with all the correct optics/ grating and actually see the results of your hard work.

Almost there........

Ken

BP, also comes down to local seeing conditions.......

Bob is still alive and well.

My hero.....I did almost five years of visual SN. Search to work with Thomson to do his SN search charts and can appreciate Bob’s tremendous skills and abilities.

A wonderful special person.

I also note the exposures were over 3 hr (!!) on a bright star............

I'm revisiting this topic.....

I found that most (All?) CMOS sensors are fitted with microlenses and the immediate  chip cover plate can vary in thickness from 1 mm to 5 mm (!!!!)

If this was a real problem then surely it would be showing up on more and more images taken with CMOS cameras?

It seems strange the the prime example here and CN is of one star - Anitak

I've never experienced this type of issue.... we do suffer more from "ripples" in our spectrographic profiles - an intensity waviness - thought to be due to either/ both the internal structure of the silicon chip or interference between the cover plate and the silicon surface.

See: 

https://www.lensrentals.com/blog/2014/06/the-glass-in-the-path-sensor-stacks-and-adapted-lenses/

http://www.astrosurf.com/buil/CMOSvsCCD/index.html

https://britastro.org/sites/default/files/attachments/SpectralResponse_WhitePaper_April09.pdf ( thanks to Robin for the link)

Is there a real problem here?????

Interesting comments here about the KAF 3200ME with microlenses: 

http://www.wvi.com/~rberry/astronomy/qsitesting/kaf3200me.htm

Quote:

Micro-Lens Artifacts

Micro lenses are tiny cylinder lenses designed to concentrate light on the indium tin oxide half of each pixel in the KAF 3200ME. Although I can imagine scattering from one micro lens to adjacent micro lenses could account for some artifacts, they may also be the astronomical equivalent of the “urban myth.”
Because I aligned my camera precisely north-south and east-west, I was not able to attribute possible low-intensity extensions along rows and columns in my images with any certainty to spider diffraction or blooming. If the effect is real, it is very small.

Many of us successfully use EQMod to control our HEQ/NEQ SW mounts. Using a EQDir cable you can bypass the hand controller direct to the mount.

You should have the latest ASCOM installed, then EQMod ......

Accessed through a planetarium program (I use Cartes du Ciel), EQMod gives you the opportunity to sync, and control the mount from a laptop etc.