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Can you guys please recommend me the cheapest equipment to detect exoplanets?


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Hi,

I want to buy equipment to detect the brighest exoplanets. What configuration and specific models do you think they have the best relation quality-price? My budget is 200 euros.

I know for sure that I will get a CCD ZWO ASI120 (not included in the 200 euro-budget), but I have no idea about the rest.

I have been recommended to get a Pentacon 200mm f/4.0 lens and EQ3-2 mount, but the mount exceeds my budget even if is second hand.

Another possibility I have been told is to get the Pentacon lens with a virtuoso alt-azimuth mount, but they have told me that I couldn't detect many transits with that type of mount.

Also, what do you guys think about the celestron powerseeker 114 eq? They told me this sucks to detect exoplanets, I guess it is due to the mount and long focal lenght.

Thanks in advance!

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Detecting the tiny changes in light betwixt the main star when transited by a planet will not be something you can do very easily.... thus lots of cost involved as the equipment will need to be very sensitive ? I admire you spirit though.

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Might be worth asking the original post writer,  what do you understand by the term "exoplanet" ??

Then we can make a start  ( I'm rather hoping there is a slight mix up in terms of ... err...  terms).

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Sounds a bit ambitious on that budget, long focal length isn't really a drawback, you need something to record the light curve as it's the only way to detect planets, you wont see them visually.

Dave

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I decided to have a crack at HD209458b as part of my final year project using the Universities 16" Meade LX200. This was back in 2004 so the CCD I used was primitive by today's standards, but even so the light curve was clear. This surprised my project supervisor, but I've since learned you don't need that much aperture after hearing about people using simple lenses, so I reckon it would be worth a shot with a 200mm lens. 

Having said this, I'd favour something like a Skywatcher 130pds, as it uses a mirror, thus brings all wavelengths of light to the same focus on axis. Using an 'apo' like the 130pds will reduce the error in your results. Also buy a mono camera rather than colour for scientific purposes! 

You'll need a way of finding and tracking the parent star, so at least an EQ3 with tracking motors. I'd favour a goto mount so once you're setup and aligned you can plug in the co-ordinates and it will goto the star in question. My only fear is a goto mount will be out of budget.

You'll also need a photometric software package so you can analyse your data and produce a curve of luminosity against time (light curve). 

I remember loving my final year project so I say give it a go. My only concern is getting hold of the scope and mount for 200, so maybe second hand?

I did know a lot more about this subject 14 years ago, but the knowledge has faded over time I'm afraid. I should imagine things have 'moved on' since then also. I'm sure someone more current on the subject will be able to offer more help :)     

P.s Just remembered, you'll need a reasonable field of view around the star so you can pick a reference star, this will allow you to see what is a change in luminosity due to a transit as apposed to being due to changes in the atmosphere. This should all be part of the photometric software package. I'm just wondering if a small AZ goto would do the job? 

https://www.firstlightoptics.com/az-goto/skywatcher-skyhawk-1145p-synscan-az-goto.html

It tracks in alt/az so there will be field rotation, but you'll only be taking relatively short exposures anyway. My 100p comes to focus with my ASI120MC, so can't think why the 1145p wouldn't, but might be worth checking. You would also need a power supply and a focus mask so you can get focus exact to reduce error further with you data.

 

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It is perfectly possible to monitor exoplanets with camera lenses - the professionals do it here!

https://hatnet.org/operations.html

Some free software for processing data is here:

https://makalii.mtk.nao.ac.jp 

As Chris said, goto will help you ensure you have the right star.  EQ mount better, but even a small alt az should be ok for short exposures.  

If you want a bit of fun before then try this https://lco.global/agentexoplanet/

Give it a go!

Helen

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2 hours ago, Lockie said:

I decided to have a crack at HD209458b as part of my final year project using the Universities 16" Meade LX200. This was back in 2004 so the CCD I used was primitive by today's standards, but even so the light curve was clear. This surprised my project supervisor, but I've since learned you don't need that much aperture after hearing about people using simple lenses, so I reckon it would be worth a shot with a 200mm lens. 

Having said this, I'd favour something like a Skywatcher 130pds, as it uses a mirror, thus brings all wavelengths of light to the same focus on axis. Using an 'apo' like the 130pds will reduce the error in your results. Also buy a mono camera rather than colour for scientific purposes! 

You'll need a way of finding and tracking the parent star, so at least an EQ3 with tracking motors. I'd favour a goto mount so once you're setup and aligned you can plug in the co-ordinates and it will goto the star in question. My only fear is a goto mount will be out of budget.

You'll also need a photometric software package so you can analyse your data and produce a curve of luminosity against time (light curve). 

I remember loving my final year project so I say give it a go. My only concern is getting hold of the scope and mount for 200, so maybe second hand?

I did know a lot more about this subject 14 years ago, but the knowledge has faded over time I'm afraid. I should imagine things have 'moved on' since then also. I'm sure someone more current on the subject will be able to offer more help :)     

P.s Just remembered, you'll need a reasonable field of view around the star so you can pick a reference star, this will allow you to see what is a change in luminosity due to a transit as apposed to being due to changes in the atmosphere. This should all be part of the photometric software package. I'm just wondering if a small AZ goto would do the job? 

https://www.firstlightoptics.com/az-goto/skywatcher-skyhawk-1145p-synscan-az-goto.html

It tracks in alt/az so there will be field rotation, but you'll only be taking relatively short exposures anyway. My 100p comes to focus with my ASI120MC, so can't think why the 1145p wouldn't, but might be worth checking. You would also need a power supply and a focus mask so you can get focus exact to reduce error further with you data.

 

Thank you for your answers!

Perfect, although I think the EQ3 exceeds my budget :(

May I know please why do you think the celestron powerseeker 114 eq is not good enough? I guess it is because of the mount.. but why?

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23 minutes ago, alpha015 said:

Thank you for your answers!

Perfect, although I think the EQ3 exceeds my budget :(

May I know please why do you think the celestron powerseeker 114 eq is not good enough? I guess it is because of the mount.. but why?

This one right:

https://www.celestron.com/products/powerseeker-114eq-telescope

-It doesn't have a parabolic mirror for a start, only a spherically figured mirror, which means despite it's reasonably high focal ratio, it still won't be that well corrected to bring all light rays from all areas of the mirror to a precise focus at a single point. Only a parabolic mirror can do this at a practical focal ratio. Look out for scopes that say 'P' after the numbers, e.g. 114p, 130p etc. The 'p' stands for parabolic and this is an important thing :) Looking out for the 'p' also protects you from accidentally buying a bird-jones design which is a short tube scope with a spherical mirror and a corrector lens in the focuser...these are generally not great scopes. 

-The mount will be very shaky, and it's not even driven so I'm not sure how you would track a star accurately for several hours whilst taking short exposures every couple of minutes to produce a light curve? You would need to add at least an RA axis motor, but going back to the first point, it would just be shaking about all over the place with the slightest breeze with such a long tube on a flimsy mount. 

If you don't want a goto mount for whatever reason, I'll have a look and see what alternative I can see for close to 200.

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This is the only scope a can think of within budget that has a parabolic mirror and will track the stars allowing for a series of short exposures to be taken:

https://www.firstlightoptics.com/heritage/skywatcher-heritage-114p-virtuoso.html

It can also be upgraded to goto!

p.s. reading the fine print, there is a bit of a caveat with this mount. The sidereal tracking automatically turns off after 30 minutes. This could be a bit of a pain if your transit is 2 hours for example. 

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52 minutes ago, Lockie said:

This one right:

https://www.celestron.com/products/powerseeker-114eq-telescope

-It doesn't have a parabolic mirror for a start, only a spherically figured mirror, which means despite it's reasonably high focal ratio, it still won't be that well corrected to bring all light rays from all areas of the mirror to a precise focus at a single point. Only a parabolic mirror can do this at a practical focal ratio. Look out for scopes that say 'P' after the numbers, e.g. 114p, 130p etc. The 'p' stands for parabolic and this is an important thing :) Looking out for the 'p' also protects you from accidentally buying a bird-jones design which is a short tube scope with a spherical mirror and a corrector lens in the focuser...these are generally not great scopes. 

-The mount will be very shaky, and it's not even driven so I'm not sure how you would track a star accurately for several hours whilst taking short exposures every couple of minutes to produce a light curve? You would need to add at least an RA axis motor, but going back to the first point, it would just be shaking about all over the place with the slightest breeze with such a long tube on a flimsy mount. 

If you don't want a goto mount for whatever reason, I'll have a look and see what alternative I can see for close to 200.

Thanks again!

The one you recommended me is sold for 208 euros in my country: https://www.telescopiomania.com/telescopios-reflectores-newton/5600-telescopio-reflector-newton-skywatcher-130900-eq2.html

But the mount is eq2 , not eq3.. the eq3 costs 270 euros in my country: https://www.telescopiomania.com/monturas-ecuatoriales-alemanas/5404-montura-ecuatorial-alemana-skywatcher-neq3-2.html 

Too expensive for my budget.. and I would prefer to buy all first hand.

The Skywatcher Skyhawk 1145P SynScan AZ GOTO looks awesone, but 300 euros is also too much for me.

With respect the celestron powerseeker 114 eq.. I understand, so, the long tube and light mount both make the telescope to shake when there is wind.. so I was thinking.. what about surrounding the telescope with a wind protector like for example this one? : https://www.decathlon.es/paraviento-quechua-azul--id_8357445.html?LGWCODE=1217907;76445;4777&gclid=Cj0KCQjw8MvWBRC8ARIsAOFSVBW5yL0AVN1yradPammRgYo-PXnSbslYe_AvoM8zGP7p9k1UlAzC2psaAgLwEALw_wcB&gclsrc=aw.ds would this make the telescope totally stable? well I guess I would need a long cable for the CCD camera to prevent further shake to the telescope.

And thanks also for the last link ; yes the virtuoso was indeed recommended to me, but apart from that 30 minute-limit to track stars, I prefer one with eq mount, if possible.

Btw I would also get a RA motor for tracking (I guess that if I align the telescope with the polar with accuracy, I wouldn't need a dual axis motor).

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The XO project used 200mm lenses to find exoplanets, http://www.stsci.edu/~pmcc/xo/equipment/  but it looks like the mount the used is a fairly high end one.

Do you have much experience in photometry? If you do then I'd say you are on the right track. If not, I recommend reading here https://www.aavso.org/ccd-photometry-guide Calibration is the most important section to read. One thing about the ZWO120 is that it does not have a cooler or temp regulator so this is going to make calibration difficult. But maybe there is a work around, like maybe taking a dark after each image while the temp is close to the temp that the image was taken with. Also the ZWO does not have a mechanical shutter so taking darks will be a bit more challenging. Maybe an automated flip-flap over the lens might do.  

Another thing to watch is saturation. The ZWO has a 12bit ADC so has a smaller dynamic range than some higher end cameras. Have to be careful not to saturate target and comparison stars. 

Actually you will need some sort of automated focus too. As the temp changes the focus will change and you will need to compensate for this. 

 

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On 15/04/2018 at 22:01, alpha015 said:

Thanks again!

The one you recommended me is sold for 208 euros in my country: https://www.telescopiomania.com/telescopios-reflectores-newton/5600-telescopio-reflector-newton-skywatcher-130900-eq2.html

But the mount is eq2 , not eq3.. the eq3 costs 270 euros in my country: https://www.telescopiomania.com/monturas-ecuatoriales-alemanas/5404-montura-ecuatorial-alemana-skywatcher-neq3-2.html 

Too expensive for my budget.. and I would prefer to buy all first hand.

The Skywatcher Skyhawk 1145P SynScan AZ GOTO looks awesone, but 300 euros is also too much for me.

With respect the celestron powerseeker 114 eq.. I understand, so, the long tube and light mount both make the telescope to shake when there is wind.. so I was thinking.. what about surrounding the telescope with a wind protector like for example this one? : https://www.decathlon.es/paraviento-quechua-azul--id_8357445.html?LGWCODE=1217907;76445;4777&gclid=Cj0KCQjw8MvWBRC8ARIsAOFSVBW5yL0AVN1yradPammRgYo-PXnSbslYe_AvoM8zGP7p9k1UlAzC2psaAgLwEALw_wcB&gclsrc=aw.ds would this make the telescope totally stable? well I guess I would need a long cable for the CCD camera to prevent further shake to the telescope.

And thanks also for the last link ; yes the virtuoso was indeed recommended to me, but apart from that 30 minute-limit to track stars, I prefer one with eq mount, if possible.

Btw I would also get a RA motor for tracking (I guess that if I align the telescope with the polar with accuracy, I wouldn't need a dual axis motor).

You would only need an RA axis motor to track if you polar align, but polar aligning will be tricky to do when the EQ2 doesn't even have a hole for a polar scope, or any kind of hole to look through to line up with Polaris. You can build a wind break which will help with the wind aspect. 

It seems that you're very much set on the power seeker. I can't recommend it, but if you want to give it a go then that is your call. I would personally save a bit more money for something a little better suited to the task at hand, but I wish you all the best, and let is know how you get on :) 

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16 minutes ago, dokeeffe said:

The XO project used 200mm lenses to find exoplanets, http://www.stsci.edu/~pmcc/xo/equipment/  but it looks like the mount the used is a fairly high end one.

Do you have much experience in photometry? If you do then I'd say you are on the right track. If not, I recommend reading here https://www.aavso.org/ccd-photometry-guide Calibration is the most important section to read. One thing about the ZWO120 is that it does not have a cooler or temp regulator so this is going to make calibration difficult. But maybe there is a work around, like maybe taking a dark after each image while the temp is close to the temp that the image was taken with. Also the ZWO does not have a mechanical shutter so taking darks will be a bit more challenging. Maybe an automated flip-flap over the lens might do.  

Another thing to watch is saturation. The ZWO has a 12bit ADC so has a smaller dynamic range than some higher end cameras. Have to be careful not to saturate target and comparison stars. 

 

 

The above is good advice, telescope and mount aside, it is really helpful to remove as many sources of error in your data as possible. Keep exposures short and use dark frame subtraction.

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6 hours ago, Lockie said:

The above is good advice, telescope and mount aside, it is really helpful to remove as many sources of error in your data as possible. Keep exposures short and use dark frame subtraction.

Thanks again! 

Btw may I ask a last question please.

Which mount is better, the skywatcher eq3-2 deluxe or the bresser eq 3-1? 

Thanks!

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4 hours ago, alpha015 said:

Thanks again! 

Btw may I ask a last question please.

Which mount is better, the skywatcher eq3-2 deluxe or the bresser eq 3-1? 

Thanks!

Do you mean this one?

https://www.bresser.de/en/Sale/Display-Items/BRESSER-Messier-EXOS-1-EQ-4-Mount-bresser.html

I've got a feeling that the Bresser has proper bearings in it's axis, and obvioulsy the steel tripod is a big improvement over the ali EQ3 one, so I would say the Bresser is better, but an awful lot of people have the Skywatcher EQ3, and there is plenty on the net about making improvements to them. 

The above Bresser is a good price for the spec with it being ex display. I've bought ex display kit from them in the past and to be honest it all looked new.

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59 minutes ago, Lockie said:

Do you mean this one?

https://www.bresser.de/en/Sale/Display-Items/BRESSER-Messier-EXOS-1-EQ-4-Mount-bresser.html

I've got a feeling that the Bresser has proper bearings in it's axis, and obvioulsy the steel tripod is a big improvement over the ali EQ3 one, so I would say the Bresser is better, but an awful lot of people have the Skywatcher EQ3, and there is plenty on the net about making improvements to them. 

The above Bresser is a good price for the spec with it being ex display. I've bought ex display kit from them in the past and to be honest it all looked new.

Thanks for your answer.

Nop sorry I was referring to this one: https://www.milanuncios.com/telescopios/montura-equatorial-eq3-bresser-256010174.htm

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14 hours ago, alpha015 said:

Sorry, for some reason it will only let me reply inside a quotation box?...........Anyway, in that case the EQ3 is much better for the simple fact that it has a hole for a polar scope. With the EQ3, even if you don't buy a polar scope you can use the hole to line up with Polaris, this will make things much easier compared to the EQ2 or the Bresser you have linked.

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8 hours ago, Lockie said:
22 hours ago, alpha015 said:

Sorry, for some reason it will only let me reply inside a quotation box?...........Anyway, in that case the EQ3 is much better for the simple fact that it has a hole for a polar scope. With the EQ3, even if you don't buy a polar scope you can use the hole to line up with Polaris, this will make things much easier compared to the EQ2 or the Bresser you have linked.

Thanks for your answer!

I will get the eq3-2 of skywatcher then.

Cheers.

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On 20/4/2018 at 22:47, Lockie said:

Good call :) 

Thanks.

Btw just quick question. What is the deepest dip (in %) from a star with mag 12 or brighter do you think it's possible to detect with the zwo asi 120 MM? is there any official page or table where I can check this kind of things?

Let's say an eq3-2 and 114 eq reflector telescope would be used.

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6 hours ago, alpha015 said:

Btw just quick question. What is the deepest dip (in %) from a star with mag 12 or brighter

I'll be honest, I don't know that exact information off the top of my head, but mean average dips tend to be around 1% in light. Maybe check out the Exoplanet Transit Database for more specifics.  

http://var2.astro.cz/ETD/

6 hours ago, alpha015 said:

do you think it's possible to detect with the zwo asi 120 MM? is there any official page or table where I can check this kind of things?

I don't think there is a table for cameras vs transit detection, not sure there is a need? I don't see why the ASI120mm wouldn't work as long as you don't saturate the chip with excessive exposure.

The camera I used to detect HD209458b was circa late 90's! Think it was an Sbig ST7.

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Scope wise, keep it short in focal length to increase the field of view on the chip. This will help with finding the star in question (surprisingly tricky), and having enough reference stars in the field of view for your analyses. 

If your budget is 200, maybe buy the mount EQ3 with RA motor, and a cheap DLSR and 200mm prime lens off ebay. Yes the DLSR is colour which isn't ideal, and the lens won't be apo so there will be a bit of error in your data, but I really do fear you won't be able to get off the ground even searching around manually for an obscure star with a long scope and a tiny chip, and never being sure if you actually have the right star! At least with the DLSR and a lens you'll have a big field of view to find the star and reference stars in question. 

You could buy a Canon 1100D and 200mm lens for your ASI120mm budget!

Thinking about it more deeply, I feel this is your only hope within budget. If you have more money yes buy a small reflector, but not one with a long focal length. 

You can see how different telescope and cameras effect field of view using the 12Dstring site:

http://www.12dstring.me.uk/fovcalc.php

Good luck :)  

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6 hours ago, Lockie said:

Scope wise, keep it short in focal length to increase the field of view on the chip. This will help with finding the star in question (surprisingly tricky), and having enough reference stars in the field of view for your analyses. 

If your budget is 200, maybe buy the mount EQ3 with RA motor, and a cheap DLSR and 200mm prime lens off ebay. Yes the DLSR is colour which isn't ideal, and the lens won't be apo so there will be a bit of error in your data, but I really do fear you won't be able to get off the ground even searching around manually for an obscure star with a long scope and a tiny chip, and never being sure if you actually have the right star! At least with the DLSR and a lens you'll have a big field of view to find the star and reference stars in question. 

You could buy a Canon 1100D and 200mm lens for your ASI120mm budget!

Thinking about it more deeply, I feel this is your only hope within budget. If you have more money yes buy a small reflector, but not one with a long focal length. 

You can see how different telescope and cameras effect field of view using the 12Dstring site:

http://www.12dstring.me.uk/fovcalc.php

Good luck :)  

Thanks!

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