Advice needed on telescope

[kecsap]

Hi,

I use Skywatcher Heritage 130P for stargazing for a year, but I am still a newbie. Now I would like to build a cheap, small setup to contribute something "scientific", e.g variable star observations. Maybe it is not possible with my conditions therefore I need some advise.

Are a Skywatcher Heritage 114P (with Virtuoso) or Skywatcher Explorer-130P (with Supatrak) good enough to take shoots on a city sky to measure variable stars (and upload the results) or some other things which has some scientific value?

I don't want to go for astrophotography with this setup at home, I use iTelescope network for that purpose.

Thanks,
Csaba

Edited September 12, 2016 by kecsap

[happy-kat]

The Explorer staright out of the box does not reach focus with a DSLR atatched (if it is the 130p version I am not sure on the longer tube length one). The primary mirror would need to be moved up the tube a bit, unless you managed to get focus using a barlow.

Generally from the great no EQ challenge thread motorised Alt-Az mounts can take exposures between 10 and say 45 seconds depending on where in the sky it is pointing before star streaking becomes too apparent.

Do you need to use a telescope would a DSLR and camera lens provide you with what you are looking to do?

Sounds interesting, how do you go about measuring variable stars

[billyharris72]

Hi Csaba,

I'm in a similar position in that I'm looking to do someting beyond "just" observing but don't quite know where to go with it. Depending on what you mean by "scientific" I think quite a bit is possible on a reasonable budget, provided you mean scientific in the sense of "scientific hobby" rather than making significant contributions to observational astronomy. That's not to say that gathering useful data is not possible (e.g. comets can still be uncovered with modest equipment) and variable star observing is one of the areas where amateurs still make a contribution. I'm looking at starting some variable star monitoring photometry myself, possibly coupled with (low res) spectroscopy.

When it comes to kit, personally I'd go with an EQ mount, and the best you can afford. For me at the moment that's an EQ5, but more would be better. Given that you're not looking at doing serious astrophotography you can probably get away with an EQ3 (I reckon you can do some simple AP on bright targets with that too, though the results will be fairly limited). I'm sure that an AZ mount of the type you mention would do the job for short exposures though.

For optics, having a high focal length is not necessarily important for variable stars, so don't overlook the possibility of using a DSLR and a telephoto lens. Secondhand M42 telephoto lenses are inexpensive, often decent quality and give nice flat fields. A 200 or 300mm could do quite a lot, for very little cash layout.

As happy-kat has said, the standard 130P won't reach focus with a DSLR, though I believe the (slightly more expensive) 130P-DS is designed to do just that (it's on my shopping list, along with a coma corrector). Alternatively, you could look at moving the mirror closer to the secondary.

Funnily enough I've been experimenting with this using none other than the Heritage 130P (by partially closing the tube). Early days yet, but initial conclusion is that it's feasible. It has two significant drawbacks in that:

1) a DSLR is fairly heavy and throws the collimation off a bit. It might be possible to brace the tube somehow, but that would lilkely make the next issue worse.

2) Focusing is interesting - most of it has to be done by sliding the tubes in and out until the image is reasonably sharp, with the finishing touches done by removing the camera (as the helical focuser rotates) and partially turning the focuser, reinsert and check, rinse, repeat etc. It's a bit frustrating, though there is a certain grim satisfaction in knowing any results you do get are despite your equipment as much as because of it.

Even so, the image quality on my first attempt was about the same as the results I've had with the Startravel 80, only without the CA and with a longer focal length. For photometry (where deliberate slight misfocusing can actually be an advantage) I'm sure this can be made to work (and it's quite fun to try in any event). Unfortunately, it won't take a coma corrector, so astrometry may not be very accurate.

That's my thoughts anyway. Hopefully something in there is some use to somebody.

Billy.

 

 

 

[MattJenko]

Variable star observing can be done with mere binoculars with practice, so your existing kit can be used for sure. While nearly all of the variable star observations in both the AAVSO and other equivalents are done via photometric CCD measurements these days, there is still some visual work being done. I know because I help volunteer to transcribe visual hand written measurements from paper observation sheets of star magnitudes into an electronic database format for entering into the wider databases from the predominantly older generation of prolific variable star observers who haven't made the electronic switch yet  

[Putaendo Patrick]

Hi, welcome to the SGL forums!

Light pollution in a big city will limit what you can observe - but there are still plenty of possibilities. Compared to many cities, Tampere is not "too" bad - but this depends on specific local conditions. If you can travel out of the city to a darker site, so much the better http://www.lightpollutionmap.info

I recommend looking at the American Association of Variable Star Observers (AAVSO) website to see what other people are doing and the equipment they are using. In particular there are three very useful manuals for visual, DSLR and CCD which you can download. https://www.aavso.org/observing-manuals

If you stick to DSLR photography without a telescope, have a look at DIY barn door mounts which can be very simple and cheap to make. Plenty of advice on the Internet, for example: http://www.astropix.com/bgda/sample2/sample2.html

 

[kecsap]

Hi guys!

Thank you for all the suggestions. I was reading more in this whole topic, because it was told on one hand that an EQ mount would be nice to have, the manual observation with binoculars work also on the other side. If both ways are okay, an AZ mount also should work in between. Looking more on ebay, I could see that I can get a telescope with motorized EQ2 mount for the same price like that Heritage with Virtuoso mount. In the end, I have chosen the latter because the EQ2 mount is just too big and not so portable. Anyway, the major part will be to start the system building, programming and I can upgrade the mount later if it is worth.

I have not told, but I will make the following system:
- An all-sky camera from a Raspberry Pi with NoIp camera+humidity sensor. I have seen a video on youtube that this camera works well for all-sky purpose with city sky.
- Wedged Virtuoso AZ mount to "simulate" an EQ, controlling via Bluetooth connection. On Windows side, there is ASCOM driver, I can drive the mount remotely.
- I am not sure if the mount can carry the Heritage+DSLR together, but the DSLR can be attached alone on the Virtuoso as a second option.

I will put this small system to my balcony and controlling from my flat.

Csaba

[happy-kat]

Great project ideas.

I can control my virtuoso mount from my tablet I have a bluetooth dongle for it. This can be used with skysafari 4 plus giving goto using the android virtuoso mount application in google play store.

The mount has a 4 kilo pay load.

I use a dslr with lens on my virtuoso and exposure range varies depending on where I point in sky (theory between 10-45 second my views are limited to go for the top end of range). Adding a wedge assumes the tracking is accurate/constant enough to manage longer exposures, that is an unknown and whether the motors cope with the angle.

[happy-kat]

Some links you might like.

link here and here

[kecsap]

11 hours ago, happy-kat said:

Some links you might like.

link here and here

@happy-kat: Do you know if the Brazilians still make the Bluetooth module? Their website is down. Do you have the email address contact to those people? Can you share with me in private message?

Do you put 4 kg payload to the mount? I read that it can handle only 2 kg.

Edited September 15, 2016 by kecsap

[happy-kat]

I'll pm details later re adaptor, there is uk seller astronomy365 do one though mine came from Brazil.

And check again where I read 4 kilos. 

Edited September 15, 2016 by happy-kat

[happy-kat]

I have so far only used my camera on the virtuoso mount, not yet decided completely if I'm going to use my heritage 130p on it as I think if rather keep the payload lower.