Paul Gerlach

Hi Steve, For some reason I don't receive any e-mail when there are new posts. Here are some tips: Use a 0.5 mm (or even a 0.6 mm) instead of an 0.4 mm. Due to the carbon fibres a wider nozzle will avoid any clogs. Bed adhesion: Hairspray on PEI surface (without the adhesion maybe to good). Other bed surfaces may also work. Haven't tried that. Bed temperature: 80C first layer, 70C second layer and onwards. Nozzle temperature: 240C For the main body: 6-8 mm brim Layer height 0.2 mm (first layer 0.1 - 0.15 mm) shell: 3 layers infill: 30% Full honeycomb (for main body) Support: not to much infill (20%) and 3-4 layers of interface with a separation of 1 layer (0.2 mm). Support from 50-60 degrees onward. Printing speed: depends on your type of printer (60 - 80 mm/sec). CoreXY printers can handle 120 - 150 mm/sec) You can print multiple objects but the threatened ones should be printed one at a time at a layer height of 0.1 mm Calibrating your extruder is essential (google for some explanation) so as to avoid under- or over extrusion. Because plastics tend to shrink when cooling down, you should use x, y compensation in your slicer. I don't use CURA myself but google for 'Horizontal Expansion CURA' to learn more. Don't use PLA for the main body as this material is transparent to infrared light and it starts to deform at temperatures above 50C. Hope this will get you started. Cheers, Paul

Although ABS is a very common filament, it has its problems. Warping due to rapid cooling is a big problem. Especially with relatively big objects like the Lowspec main body. I Use Green Tec Carbon from Extrudr. It has little warp and is, as the name suggest, filled with carbon. Paul

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

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

Well... back in 2012 I made this one... 😂

Installation of the roof. Used some painters tape because I'm not very good when it comes to silicone sealant 😅. The black 'skirt' is to cover the small opening.

This evening (they get noticeably shorter) I installed some elements of the roof. The telescopic rails, side panels and roof support. Al the brow-black parts are 3D printed.

The frame is made out of aluminium 30 x 30 mm profiles. 1200 x 1200 mm foot print, 1300 mm height. Walls are of 6 mm thick HPL panels. Roof side panels of the same HPL. The top 3mm HPL sandwiched with aluminium.

After work, finished the sliding door to gain access to this small telescope housing. Next will be the roof.

Found some time today to build on my mini observatory.

Another step. Placed the Electricity cable. First pour of concrete for the floor. A foam border is to keep the concrete from the floor away from the concrete pier so no vibrations can be transferred. Tomorrow I'll place the rebar and do the rest of the concrete.

Hi Rodolphe, Those are concrete palisade (120 x 15 x 15 cm). I matched it with the footprint of the observatory (120 x 120 cm).

It's a electrically powered pier from Pier-Tech. I bought it about ten years ago and will probably never part with it 😄

No automation of the roof. I'll simply open and close it by hand. The pier can be extended lifting the telescope out of it's enclosure. Telescope will be operated remotely.

After a few years without one I finally started the build of a new shelter for my telescope. Here a few pictures of the work in progress. Cheers, Paul

Valerio, Are you sure you've placed the slit disc in the correct orientation? Meaning that the mirror surface is facing the inside of the spectroscope. If not, it could be that the bright light is being reflected between the two surfaces of the slit disc.

Focusing on dust that's on the slit disc is not a good idea. The slit itself lies 1 mm lower than that dust. Be aware that the reflective surface containing the slits should face towards the optics inside the LowSpec and not towards the telescope. I would suggest to remove the slit assembly and use a laser collimator at the telescope end of the Lowspec to see if everything lines up. the laser should strike the mirror, collimator lens and grating in the centre. If not, you can adjust the 'big' mirror by slightly loosening the centre screw and use the three grub screws to tilt the mirror in the correct position. Don't forget to tighten the centre screw afterwards but make sure not to over tighten it. Then put the slit assembly back and remove the camera lens (first loosen the little grub screw at the side of the focus assembly). Close the lid and point the lowspec at a bright light source (not the sun!!). Use a small scope (telescope finder, binocular, etc.) that is focused at infinity and use that to look at the grating from the camera opening of the Lowspec. Now turn the micrometer screw inwards until you see an image of the slit itself (zero-th order) in white light true the little scope. Loosen the screw of the collimator lens a bit and use the screw driver to move the position of the collimator lens until you see a sharp image of the slit. Tighten the collimator screw and place the camera lens back. When you attach a camera to the Lowspec and notice that the spectum is off centre, you can adjust the 'big' mirror again to place the image back in the centre.

They are just dust caps. In case you don't use the LOWSPEC and want to store it.

Hi Valerio, Yes they are the same. Paul

Looks very good! Just to clear things up; T2 thread is not the same as M42. Although they have the same width (42 mm) they have a different pitch. M42 has a pitch of 1 mm and T2 a pitch of 0.75 mm. The illuminator is only necessary at very dark locations. At urban locations and good guide camera you can easily make out the slit against the sky background. Also you can mark the slit position in guide software like PhD during daytime and use that at night. So if you don't use that back illumination feature simply leave 16_jeulin_slit_illuminator out. It will not influence the spectrum. Paul

Hi Graham, There are two holders for the collimator provided. For f/6 and f/10. If you use the lens holder that is stopped down to f/10 you will lose light as part of the f/8 light cone will be blocked. So use the f/6 holder. Or better yet, use the f/8 collimator holder I've included below and also just uploaded to the Thingiverse page. Success with your build! Paul 08_holder_collimatorlens_f8.stl

Yes, I think the 600 l/mm grating would be a fine choice.

Hi Valerio, That looks okay. But I can buy several for that price.... Have a look at this. You need the SR4 model. Mabe their German branch will ship to Italy. If not I can order it as I'm planning to order a few anyway. With shipping cost you still save some money. The 600 l/mm grating would be a great compromise indeed. In fact anything from 1800 l/mm downward will work. The LOWSPEC (@ 300 l/mm) struggles with getting the whole visual spectrum into proper focus anyway (especially when operated faster than f/10) and if you want to do some higher resolution you'll have to work at f/10 and use a 30 x 30 mm grating in order avoid lost of efficiency. The 25 x 25 mm grating at 1800 l/mm is just a bit to small. Regards, Paul

Hm, no. Sorry. I can upload a new version but that one is not as 'clean'. I've recently made some changes to other parts e.g. the guide lens holder and I have to make changes to the manual to reflect them. But if it helps I can upload it here for you. Paul