Thalestris24

7 minutes ago, Bajastro said:

After the calibration of axis RA in my mount I calibrate GoTO usually with using one star. Next I center first star with visually observation in finderscope 8x. Important is moving on the same side of sky where was calibrated star for GoTo system. Becasue after rotating mount on the opposite side of the sky usually scope isn't pointed on a particular star.

I'm using HEQ5 mount with Rowan modification kit.

Ok - so that gets a particular star close to the slit?

1 minute ago, Bajastro said:

@Thalestris24 I use built-in Low Spec guide module with achromatic lens with 30 mm focal length and ASI120MM Mini.
I don't need any external guide scope.

Similar to my qhy5l-iim then - same sensor. How to do you get a particular star on the slit? I'm using an e-finder - a 70/400mm scope with a 178m camera plus plate solving. Maybe you have a much better mount and alignment than I have?

Louise

11 minutes ago, Thalestris24 said:

Well, I just attached the Lowspec to the imaging scope and got it more or less focused. I think it still is quite a small fov. I took some pics of a pylon:

Look pretty similar in scale to the Coma Berenices comparison. Of course, substituting the Lowspec for the qhy5l-ii means the two images are no longer aligned as before. So I'll have to do that all over again...

It doesn't look like there will be any clear sky tonight

Louise

Just did a quick align:

Close enough, I hope! I suppose I'll have to keep doing the alignment...

Louise

3 hours ago, Thalestris24 said:

So I did manage to get some images of some stars in the Coma Berenices cluster last night, which was good. But then I had a moment and thought "Oh, wait a minute..." - am I thinking about this wrong?? I've set up with the qhy5l-ii as an imaging camera in the 115/800mm scope. But in the Lowspec I'm using the qhy5l-ii with a 31mm lens focused on the plane of the radial slit and looking at the image projected onto the surface by the 800mm scope. These two situations are not the same, are they? Or are they? I should know but my old brain gets stuck in the groove sometimes! I'd previously thought I would only see a 20' x 15.5' view of the sky via the guide cam but that can't be right. Surely it will see the size of the image effectively projected onto the surface of the Ovio. I don't know exactly how you calculate the effective fov of the guide cam and lens - it must be more akin to macrophotography with a small sensor? There is probably a calculator somewhere which will give me a better idea of actual fields of view and dimensions of images...

I should probably attach the Lowspec to the scope and see what I can really see in practice! At least I've proved I can closely align images with a small fov!

Louise

Well, I just attached the Lowspec to the imaging scope and got it more or less focused. I think it still is quite a small fov. I took some pics of a pylon:

Using qhy5l-ii:

nb - slit across the middle! I will align it along RA (or maybe DEC) at some point.

178 on Travelscope:

Look pretty similar in scale to the Coma Berenices comparison. Of course, substituting the Lowspec for the qhy5l-ii means the two images are no longer aligned as before. So I'll have to do that all over again...

It doesn't look like there will be any clear sky tonight

Louise

27 minutes ago, Bajastro said:

Hi everyone,

I'm new in this forum.

I also built Low Spec spetrograph designed by @Paul Gerlach in second version. I use 1800 l/mm holographic diffraction grating:

I received first profiles of spectral lines few bright stars in higher resolution, examples:

But I have similar problem as @drjolo . Image of star in my guider module is very low quality.

See below:

I know that f/4 Newtonian telescope isn't optimal for Low Spec. Soon I will buy Barlow 2x.

Marius

Hi Marius

Welcome to the fold! Your Lowspec looks very neat! What guide scope are you using? Your guiding doesn't look too bad - much better than I'll be able to achieve. Looks like you just need to collimate? But I know nothing! I've not done a star spectrum yet but am getting there...

Louise

So I did manage to get some images of some stars in the Coma Berenices cluster last night, which was good. But then I had a moment and thought "Oh, wait a minute..." - am I thinking about this wrong?? I've set up with the qhy5l-ii as an imaging camera in the 115/800mm scope. But in the Lowspec I'm using the qhy5l-ii with a 31mm lens focused on the plane of the radial slit and looking at the image projected onto the surface by the 800mm scope. These two situations are not the same, are they? Or are they? I should know but my old brain gets stuck in the groove sometimes! I'd previously thought I would only see a 20' x 15.5' view of the sky via the guide cam but that can't be right. Surely it will see the size of the image effectively projected onto the surface of the Ovio. I don't know exactly how you calculate the effective fov of the guide cam and lens - it must be more akin to macrophotography with a small sensor? There is probably a calculator somewhere which will give me a better idea of actual fields of view and dimensions of images...

Anyway, fwiw, here are a couple of images of the cluster comparing the 178 and the qhy5l-ii:

178 1280 x 1024:

qhy5l-II:

16 Com 178 1280 x 1024:

I should probably attach the Lowspec to the scope and see what I can really see in practice! At least I've proved I can closely align images with a small fov!

Louise

Have just about managed to plate solve and check that the 178 and qhy fov's are pretty much lined up. Transparency has been poor so not easy to get enough stars to do the plate solve, and exposures have needed to be rather long. I'm staying up and running and I'll try again later if it's clearer. Wish I could pick up more stars from here... The Coma Berenices cluster is quite bright and will be about later so hope to try on that.

Louise

28 minutes ago, drjolo said:

If you align spectroscope slit along E-W direction, then tracking and guiding errors will move star along slit. You will not loose light then when star moves off the slit, only the spectrum will be little bit higher.

Yeah, I'll try it when it comes to attaching the Lowspec to the scope.

Louise

8 minutes ago, Paul Gerlach said:

Good work Louise! Perseverance pays-off in the end.
Recently bought a second 3D printer. A more mainstream one (Sidewinder X1) to get a more realistic picture off what these machines produce. Kinda strange to realize that I can start a print farm with five of these for the money I spend on one Felix Pro 3....

Paul

Thanks! I don't know much about 3D printers - I only bought the Ender 3 Pro to print the Lowspec! Maybe I'll find some other things to print/make - who knows.

Louise

I managed to get the Ovio lock ring reprinted - and screwed in! Woo! So, hopefully, turning the slit selector will work properly now. I nearly threw the thing out the window trying to get the slits lined up with the corresponding size marker! Gave up in the end, and just settled for the slit lining up with the holder opening. I've not actually tested it again yet. I could just about make out a couple of stars last night so got the 800mm/qhy5l-ii and 400mm/178m focused on some stars. I successfully plate solved with the 178 using SharpCap. Currently, the AVX PA must be way off and it's nowhere near balanced at the moment. However, I couldn't get the 178 image properly aligned with the qhy5l-ii image. It's really not an easy thing to do... But today I managed to get a much better alignment (than I previously had) on an electricity pylon. Everything's seems easier in the day. It's supposed to be clear later tonight (not that I believe the forecast) so hopefully I'll be able to try again to get the two images aligned. The 800mm scope image is about 20.6' x 15.5' - quite a small area of sky to align the 400mm scope to. I set a roi on the Travel Scope 70/178m to be 1024 x 768 and that pretty well matches the image size of the qhy5l-ii on the apo, so used that roi for fine adjustment. I should have done that before, really... Anyway, if it is clear (but also too cold for me...), I might even try to take some images, but at less than an arc sec per pixel they are likely to come out rather fuzzy especially as my guiding is only +/-4". The Travel Scope 70/178 at 3072 x 2048 should maybe appear better even though the scope optics are poor (the scope only cost me £39 off Amazon 4 1/2 years ago - bargain! ).

Louise

50 minutes ago, NenoVento said:

Thanks @Thalestris24 (Louise) for your comments, yes, 380nm is very close to the visible spectrum (400-700 nm) and also the filter seems to have an IR window (that reach to about 30%) overlapping the 700 nm zone... I guess that it won't probably work with Venus, or at least not in the way that the baader and the rest do. However, since you have one of them, maybe you could give it a go 😉.

Although the ZWB filters are indeed cheap, in my case, since I have to get two adapters (at least for the M49 one, I haven't found an M42 one), their added costs makes this a rather pricey experiment for me to pursue right now, really...

Best regards,

NV

Hi

To be honest I can tell it wouldn't be very useful from the transmission spectrum. The visible (violet) and near ir it lets through would drown out the uv. I'm afraid I don't do planetary and have no view of Venus anyway.

Cheers

Louise

11 hours ago, NenoVento said:

Hi all,

As you know, baader, astrodon and idas UV-pass filters, which are the ones used for imaginh Venus' clouds, are quite expensive. However, by searching on the Inertnet for similar (at least by name)  kind of filters, I came across with a possible alternative:

https://es.aliexpress.com/item/32969203564.html

According to the provided transmitance graph, the filter seems to reduce visible light considerably, while leaving UV and some IR to pass:

Honestly, being so cheap, I'm really tempted to try one. Unfortunately, they don't have an M28.5 version that I can directly thread to my cameras or to my 1,25" filter wheel so, in order to find a way to use it, and assuming that being advertised as a 48mm filter it will be able to slide inside a 2" barrel, purchasing the adapters that my scope requires (which, if I am not mistaken, are a SCT female to 2" and a M49 female to M48 male so as to thread the filter into my 2" barlow) will increase the overall costs considerably, reaching to about 26 GBP for the whole set.

What do you think?.

Regards,

NV

 

 

I bought a 42mm diameter version of one of these but I don't recall doing anything astro with it. A problem is that mono or full spectrum sensors tend to be more sensitive to the near ir than to the violet/near uv. Plus 380nm can still be considered to be in the visible spectrum. Pure UV pass filters are hard to make so that's reflected in their price, plus not so many made because not many people bother with them. Since the zwb ones are cheap, maybe still worth a play if you fancy.

Louise

Just now, Paul Gerlach said:

You know what? Turn that ring upside down. Print it 180 degrees rotated so that the side you you are going to thread in is on top.

I have tried that before. I'll have another look tomorrow.

10 minutes ago, Paul Gerlach said:

Louise,

Try to print at a layer height of 150 micron (0.15 mm) and set the first layer also to that height (or 100%). Set the first layer 'extrusion width' or 'layer width also to 100%. Print slow (say 30-40 mm/sec).
If you still have no success try printing with a raft. Set the raft to two layers and three top layers at 100% infill set the distance above the raft (the first layer of the actual object that's being printed) to 0.15 mm. Again set the layer height of the print to 150 microm (0.15 mm).

Paul

Hi Paul

Thanks for the suggestions. The first paragraph is what I do except at 0.12 layer height. Is there a reason for setting it to .15?

I'll try the raft option but I don't understand why it's been printing the way that it has. I feel like maybe I've been doing something stupid...

Louise

2 hours ago, Thalestris24 said:

It looks like I'll have to print yet another lock ring... It's not been coming out right even though I did the extrusion calibration. The first few layers print bigger than the rest so parts have a miniature skirt ('skirt' is not set in Cura). If anybody knows what's causing this printing problem I'd be grateful for any suggestions/help!

Cheers

I wonder if the printing problem is a Cura setting, something to do with pla, or something to do with the Ender 3. I noticed Paul mentioned he prints threads with polycarbonate but he has a different printer also. 

Louise

3 minutes ago, Merlin66 said:

Louise,

Can't help with the printer problems....

I'm a little surprised to see the differences between your slit image and Paul's image....taken with the same QHY5 II camera.

I assume you both use the same focal length guider lens???

 

Hiya - not the same. Paul has qhy5-ii, I have a qhy5l-ii - smaller pixels.

Louise

On 11/01/2020 at 22:14, Paul Gerlach said:

Louise,

Just as a reference; I made a quick snapshot of the view of a QHY 5-II camera on the slit.

Paul

I just readjusted my guide cam to get the slit horizontal. As mentioned before, I can't fit all of it in the fov using a qhy5l-iim. This is about the best I could get (excuse the sensor dust!):

That's a 20um slit. The position of the slit isn't stable - the rotation mechanism isn't working properly. It looks like the Ovio slit isn't necessarily moving in tune with the selector i.e. it's slipping. Annoyingly, it was fine before I reprinted the moving part but now the movement is sticky rather than smooth. I guess the lock ring isn't gripping the slit properly but I haven't been able to get it to properly screw in - had to snap it in place. It looks like I'll have to print yet another lock ring... It's not been coming out right even though I did the extrusion calibration. The first few layers print bigger than the rest so parts have a miniature skirt ('skirt' is not set in Cura). If anybody knows what's causing this printing problem I'd be grateful for any suggestions/help!

Cheers

On 12/01/2020 at 17:17, Thalestris24 said:

I managed to get the Travel Scope mostly sorted yesterday and today. Had to do some guide ring musical chairs and ended up with a pair which fit the body of the scope but are rather on the tight side... However, it looks like it's possible to more or less centre the two fields of view using a tv aerial on a nearby roof. The hard part will be getting it down to the window of the qhy5l-ii and keeping it there. At the moment I just have a Canon 1100d mounted on the 115mm scope. I've managed to roughly centre the Travel Scope + 178m in the dslr fov. I need to tighten the bolts holding the guide rings. I'll swap the Canon for a qhy5l-ii tomorrow and see what I can do. Trying to get it spot on will probably drive me nuts...

Louise

Well, in the end I decided the guide rings weren't big or stable enough so I dug out a pair which were rather too big... But I substituted one of the adjustment knobs with a long bolt on each ring. Seems to work a lot better now and I've been able to centre the guide scope fov with that of the imaging scope. Also found out that by using mono8 rather than mono14 in SharpCap I was able to access the image flip which is useful. It won't matter for plate solving but it would have been nice to be able to flip the 14 bit image. I don't know why it's not available in SharpCap but I posted a query on the forum.

Louise 

10 minutes ago, Tomatobro said:

Having watched plate solving in action I want to give it a go but I have a question regarding connectivity.

I use Charles Du Ciel and Sharpcap pro. My question is can I connect the mount via EQMOD to both Sharpcap and CDC at the same time if both software's are open and running on the same laptop? I am looking download an image from my ASI1600, plate solve using Astro Tortilla and have CDC update its position.

 

Hi

Yes, no problem - that's what Ascom is for . You just need to complete the appropriate SharpCap hardware settings. If you already have Astrotortilla and required index files installed, SharpCap seems to recognise that and does the plate solving on request. It doesn't seem to open Astrotortlla in order to work - it's all done from the SharpCap interface. You can set it to auto access the mount via Eqmod on startup. However, you need the mount powered up and connected.

HTH

Louise

ps yes, Cartes du Ciel or Stellarium are better than Charles du Ciel  

1 hour ago, Paul Gerlach said:

Louise,

It's been a while for me that I did some actual spectroscopy on stars. Hopefully will be up and running again this year.

I used a e-finder made up off a QHY 5-II with a 1:1.4 25mm c-mount camera lens from Ebay and mounted that on the rail the telescope was mounted on. That way I was sure that there was no flex.
During day-time I aligned the e-finder roughly  with the telescope. At night I slewed the telescope at a bright star and centred it on the slit. I used EQMOD together with Chart du Ciel so I did a 'SYNC' on that star. Then I realigned the e-finder (with the help of the electronic cross hair of PHD) at the star. Checked if the star was still on the slit and repeated the process until everything was aligned.

When slewing to a faint target I first 'hopped' to a nearby bright star and did a SYNC. Or even three stars surrounding the target and synced on those (creating a correction map for the mount) before slewing to the target which I then identified with the star map from Chart du Ciel.

 

Paul

Hi Paul

I have a gpcam3 178 on a Travel Scope 70 (fl =400mm) which I've previously used as a guide scope though the 178 is new. Using plate solving I expect to be able to get it close to centred on a target. But it will have to be precisely aligned with the centre of fov of the imaging scope (fl=800mm), and the target will have to be visible in the fov of the Lowspec guide cam in order to be able to nudge it on to the slit. The mount is an AVX so no eqmod. I can't properly do a star align as I only have a limited view of the sky in the East via an open window. I've usually managed to find dso targets ok with plate solving but there is always an initial positioning error. Getting a particular star on the slit will be challenging but hopefully doable. The AVX isn't the best mount for doing this procedure but I'll see how it goes.

Cheers

Louise

I managed to get the Travel Scope mostly sorted yesterday and today. Had to do some guide ring musical chairs and ended up with a pair which fit the body of the scope but are rather on the tight side... However, it looks like it's possible to more or less centre the two fields of view using a tv aerial on a nearby roof. The hard part will be getting it down to the window of the qhy5l-ii and keeping it there. At the moment I just have a Canon 1100d mounted on the 115mm scope. I've managed to roughly centre the Travel Scope + 178m in the dslr fov. I need to tighten the bolts holding the guide rings. I'll swap the Canon for a qhy5l-ii tomorrow and see what I can do. Trying to get it spot on will probably drive me nuts...

Louise

6 minutes ago, Merlin66 said:

Louise,

Spectroscopy 201.....moving from a transmission grating to a slit spectrograph....

Practise, practise, ......

When you start to record stellar spectra you'll find a new world of issues/ problems/ concerns etc etc etc.

The main thing at the moment is to get comfortable with acquisition and processing.....

Oh dear, that doesn't sound good... If it gets a lot harder than with a Star Analyzer then I'll probably lose patience and abandon it, I'm afraid.. For me, it's just a hobby, something interesting to do to pass the time. I've already pretty much given up on dso imaging - I've not even done any live stacking/eeva since the beginning of September. I think I've lost my imaging mojo I will give the star spectroscopy a go though.

Cheers

Louise

2 hours ago, Merlin66 said:

Louise,

It's normally much easier to orientate the slit horizontal or vertically in the guide camera, this makes it easier to judge which way to nudge stars onto the slit and maintains the RA and Dec direction for acquisition.

The slit gaps are 6mm long.

The guide FOV will be constrained by the size of the visible slit plate and the focal length of the scope being used. You can roughly estimate your guide FOV by measuring the slit length on the guide image to get a scale mm/pixel. In my case due to the slit cover plate I have an opening/ FOV of 8mm x 6mm. 

Using CCDCalc (see image) this gives 9.8 x 7.4 arc min coverage.

You want to achieve as good a focus as you can on the slit gap... then when positioning a target star it also should be in good focus (using the scope focuser).

 

Hi Ken

Yeah, re slit orientation,  you said before. I was just trying to see if I could get the whole of the slit in the guide cam fov, but couldn't. Then I was using the 500mm mirror lens but couldn't get a sharper focus than the screen grab of the street lamp. It should be slightly better with the proper scope as it's fitted with a usb focuser. Mind you, I've never been able to get a definite, sharp focus of any target. I think that's a combination of low target altitude (not much more than 30-35 deg), building thermals, and usually poor transparency and poor seeing. Of course, I'll do my best when the time comes!

I think I'll get confused if I have more than one star on the slit so I'll just try and choose stars where that won't happen. Mind you, I suppose the majority of low magnitude stars' spectra are catalogued anyway. At the same time, imagers do keep imaging the same targets over and over...

Cheers

Louise

7 minutes ago, drjolo said:

In this case I think you will just have two spectra that you can process separately. You may select both stars regions and analyze separately.

Today I designed and printed simple Relco SC480 starter holder to LowSpec - I attached the models and the source file. It requires to drill 12mm diameter hole in the LowSpec cover - in the optical axis, near to telescope inlet. Then holding element needs to be glued into this hole ( I used superglue ). The limiting resistor for starter is placed in the AC plug. Here are some photos:

  

  

Starter can be put into LowSpec and secured with nut. Then after calibration it should be removed, there is another nut to cover the hole, and also safety enclosure for starter. I tested calibrating of Sun spectrum using SC480 in this holder, and I was able to measure Sun spectral lines positions with 0.15nm accuracy (600 l/mm grating, about 0.4nm FWHM). This starter should also help to focus main camera, when real target is very faint.

 

Hiya

I didn't realise the Relco bulb was so small! The spectrum looks similar to the (bigger) Sylvania (for 70W tube) bulb I recently tried - plenty of peaks at the blue end . However, I don't think the Relco is available in the UK anymore - I didn't come across any when I was searching. I have some 70-125W bulbs to try out. I kept my holder a simple push fit but I'll have to see how it performs in normal use. I thought that as it only has to be in for a short while the placing and removing of it should be fairly quick and easy. Anyways, a minor point. With the 12V DC - AC inverter I'm using, you can just as well keep the resistor in the box with the inverter but I had also originally thought about putting it in the mains plug as you've done. Are you going to use the Lowspec with your Meade F10? Can I ask what the screws are for that I can see looking through the hole at the scope end? I'm assuming you've done a modification?

Louise

Tried it out with the 500mm lens again - fov calc gives 33' x 24.75' and 1.55"/pix. Of course, I plan to put the Lowspec on the 115mm scope which will give 20.62' x 15.46' and 0.97"/pix.  Here is a quick tryout on a street lamp (unlit!) with the 500mm lens:

I used EZPlanetary to take that (more control over exposure), and the view is 75% of full. Very difficult to focus via the reflective surface but I guess you don't need sharp focus for guiding. I'm thinking the guide image will be fuzzy at 0.97"/pixel anyway.

I'm wondering how you manage if you can't avoid having more than one star on the slit? I suppose you have to just go to a different star...

I'll try the Lowspec out on the proper scope soon-ish .

Louise