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Posts posted by Merlin66

  1. Lawrence,

    Doesn't do any harm leaving it on the PC - you'll never use it.

    Make sure you have the latest ASCOM installed, and the EQAscom files.

    Best used with a planetarium interface - I use Cartes du Ciel.



  2. Jagho,

    The original LowSpec was designed around a 45 degree angle.

    Not sure what it finally became - Paul can confirm.

    (Note: this needs to be included in the SimSpec3D spreadsheet.... If correct, then the 30 x 30 mm grating with 1800 l/mm would be OK at f7.5))


    • Thanks 2

  3. Louise.

    The eFinder will get you to the target area..... the guider will give you a view of the slit position. I don't think you'll have any difficulty working between them

    Start with a bright star target....once you see what's happening -you'll be OK.


  4. The target star just needs to be visible in the guide FOV, not necessarily spot on the middle.....you do have a lot of lee way......

    Your guider field of view will be much larger than mine!!

    When you try it for the first time I'm sure you know what I mean.



  5. Marius,

    Re using a barlow...

    Caution, as you know the magnification varies with the back focus distance, when adding the spectrograph the slit plate will be probably further back than normal (with an eyepiece) and the magnification higher.

    Also consider how to give the instrument some support - to maintain the alignment on the optical axis.

    I occasionally use a x2 Powermate (with my Genesis f5) and use the T thread adaptor to improve rigidity.

    On the C11 I added a support bar to hold and align my Spectra-L200.


  6. Louise,

    I think you are worrying unnecessarily.....

    You'll find it easy to centre the star in the guide slit plate - trust me!

    Your LowSpec will work at f7 and give acceptable results - My Spectra-L200 was designed for a maximum of f7 but I have used it many times with scopes down to f5 and still obtained useable results.....

    I think you'll be pleasantly surprised when you get your first stellar spectra! Just remember to start with an A type star......


  7. Louise,

    Think of the reflective slit plate as a on- axis guider or a star diagonal. All it does is reflect the FOV at the slit position.

    The transfer lens - depending on the spacing between the slit plate and the final guide image then acts as a reducer - giving a slightly larger FOV in the camera. As far as I can see the reduction is x0.72.

    The actual guide FOV will depend on the area of the slit plate visible to the guider, the reduction factor and the guide camera chip size.

    In my case the slit plate has a front cover, with an aperture of 8 x 6 mm, centred on the slit gap. This effectively limits the actual area of the sky visible ( the camera FOV is much larger, but obviously blocked by the cover plate!)

    In my C11 @ f10 I get 9.8 x 7.4 arc min coverage.

    I can easily put a target star close to centre in the 60/220 eFinder and find the same field in the spectrograph guider. If you use PHD2 you can set up the virtual slit and nudge the target into/onto the slit gap.

    Much easier than you think.


  8. I agree with John. Trying slumping a couple of 12" disks, one was about 6mm thick the other 10mm (?) Used the services of the local ceramic group and their Kiln.

    Making a "proper" mould to slump into proved difficult, temperature control/ annnnealling became a PITA!

    Supporting the disks for grinding - sand bags/ air bags/ various disks of carpet didn't work for me.

    An alternative was to vacuum distort a thin blank (which already had a "reasonable" finish) - supported on an edge O ring within a closed cell and hand vacuum pump connected to the rear. Yes, I think it would have eventually worked, getting around f10.

    Don't even think of stretching a Mylar mirror and vacuum!!!!!


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