Jump to content

  •  

CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.

Photo

First experience with GSO 8" dob

  • Please log in to reply
16 replies to this topic

#1 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 02:08 AM

Finally, after 4 months of wait (monsoon started to wear off), I got to experience the night sky with my dob.  The view was breathtaking. I would like to thank you all the CN members who have suggested this telescope. (https://www.cloudyni...irst-telescope/
 

Due to lack of experience, I could observe only Moon, Jupiter, and Saturn. The sky is still a little bit hazy with clouds so I could not find any of the DSOs. frown.gif

 

 

I have got few questions now:-

  1.  When I watch Altair or Vena with my 30mm eyepiece, I see fine stricks of light coming out of them. Did I collimate my telescope wrong? primary.jpg primary secondary.jpg secondary
     
  2. I have a 2" 2X Barlow, I am able to use that with my 30mm, 12mm and 9 mm eyepiece to focus Moon and its look great. But when I try to use the same combo with Saturn, I fail to bring it into focus.
     
  3. What is the purpose of 35mm extender?
     
  4. What is the purpose of a fan at the base of my dob? I live in Purulia., India  (23.34°N 86.36°E)
    Climate:- https://en.wikipedia...istrict#Climate . Do I need to use the fan?
     
  5. What are easiest DSOs to watch(and find in a hazy sky) for an amateur with 8" Dob?
     
  6. What is the proper procedure to clean eyepieces?
     
  7. Could anybody help me to find the extent of light pollution in my area? And what are possible DSOs, which can be seen?
     
  8. While observations, I found that objects are not appearing in an inverted manner which I expected but the image is inverted plus rotated to an angle which is odd. What could be the possible reasons any suggestions?

Thanks and Regards


Edited by rahulm, 25 September 2017 - 09:59 AM.


#2 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 02:14 AM

2 failed attempt to take pics of moon using my Redmi Note 3
IMG_20170924_180010_HDR.jpg

 



#3 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 02:15 AM

IMG_20170924_180233_HDR.jpg



#4 earlyriser

earlyriser

    Viking 1

  • *****
  • Posts: 640
  • Joined: 08 Nov 2016
  • Loc: Cincinnati

Posted 25 September 2017 - 05:48 AM

I can't tell from the pictures, but it is normal to see four diffraction spikes emanating from bright stars. They are caused by the vanes supporting the secondary mirror.


  • paul hart likes this

#5 gitane71

gitane71

    Viking 1

  • *****
  • Posts: 704
  • Joined: 16 Jan 2012

Posted 25 September 2017 - 05:55 AM

I wouldn't call those pix of the moon 'failed attempts' !!  For the first night out, I think they are pretty Good !!  My first couple rolls of film (it was a While ago!) had Nothing at all !  I enjoy that crater chain that includes Furnerius, Petavius, Langrenus and Vendalinus !  I think you caught it pretty good ! 

For a good deep sky object, in the night, M13 if possible, in Hercules.

In the morning, try M42, in Orion.  

Have fun !!  



#6 macdonjh

macdonjh

    Vanguard

  • *****
  • Posts: 2239
  • Joined: 06 Mar 2006

Posted 25 September 2017 - 08:23 AM

I can't tell from the pictures, but it is normal to see four diffraction spikes emanating from bright stars. They are caused by the vanes supporting the secondary mirror.

Agreed.  Diffraction spikes in your scope will be 90 degrees apart, quite sharp and all the same brightness.  If you're having collimation issues, what you'll see when your view is as focused as you can make it is fuzzy blurring on one side of where the star image is.



#7 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 09:04 AM

I can't tell from the pictures, but it is normal to see four diffraction spikes emanating from bright stars. They are caused by the vanes supporting the secondary mirror.

Is it something I should be worried about? Is it possible to remove them? After you mentioned them, now I remember that I see those spikes in bright stars only. Spikes don't appear in dim stars or stars which I can't see with naked eyes.

Any suggestions to my other questions?



#8 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 09:19 AM

I wouldn't call those pix of the moon 'failed attempts' !!  For the first night out, I think they are pretty Good !!  My first couple rolls of film (it was a While ago!) had Nothing at all !  I enjoy that crater chain that includes Furnerius, Petavius, Langrenus and Vendalinus !  I think you caught it pretty good ! 

For a good deep sky object, in the night, M13 if possible, in Hercules.

In the morning, try M42, in Orion.  

Have fun !!  

Thanks!!!!! I will surely try to look for M13 though I tried to find M22 find M22 but couldn't find.   I will definitely watch M42.

Any suggestions to my other questions?



#9 Hesiod

Hesiod

    Surveyor 1

  • -----
  • Posts: 1970
  • Joined: 13 Jan 2013

Posted 25 September 2017 - 09:24 AM

1) 4 rays looking an "X"  are the diffraction spikes from the secondary mirror holder

 

2)it is likely bad seeing (e.g. the atmosphere is not steady, but there is a lot of turbulence, like boiling water in a pot)

 

3)to add those 35mm to the drawtube and attain the focus with certain equipment

 

4)to speed up the cooling of the primary mirror; ideally it should have the same temperature of the surrounding air. If there is a therml gradient between night and day, or between the storage site and observing site, it is indeed helpful; it may be useful also if the air temperature drops during the night

 

5)I suggest to download and install Stellarium or SkyChart (the former is easier to use, the latter is more powerful) and/or to purchase a small pocket atlas of the night sky; in any case,between Aquila and Sagittarius there are a lot of very bright and beautiful DSOs (the Lagoon nebula and Omega Centauri are among the brightest)

 

6)I use either distilled water and a droplet of detergent for dishes, or lens cleaner (those for LCDs or for photographical lenses); before I blow away the dust with a small dust blower (as those sold with camera cleaning kits), then dab the eyepiece with a cotton disk slightly damp, and blot the eyepiece with another dry disk. NEVER rub.

 

7)it is easier than you think: get a good star chart, choose a constellation and look at the faintest star you can see by the naked eye.

As a rule of thumb, if you can see the Milky way, the your sky is quite good

 

8) well, the inverted part relates to the horizon, but DSOs are not squared to our horizon...this is why nobody really cares about the fact that astronomical telescopes provide an inverted view (btw, some DSOs look "right" only with "inverted" telescopes, e.g. the notorious Swan Nebula is topside down in my refractor with an astronomical prism)



#10 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 09:27 AM

 

I can't tell from the pictures, but it is normal to see four diffraction spikes emanating from bright stars. They are caused by the vanes supporting the secondary mirror.

Agreed.  Diffraction spikes in your scope will be 90 degrees apart, quite sharp and all the same brightness.  If you're having collimation issues, what you'll see when your view is as focused as you can make it is fuzzy blurring on one side of where the star image is.

 

Well, all those spikes I see are directed to 1 quadrant. They are not 90 degrees apart. Can I remove those spikes?
Sorry I couldn't understand what you said about the collimation issues.


Any suggestions to my other questions?
 



#11 drneilmb

drneilmb

    Ranger 4

  • *****
  • Posts: 395
  • Joined: 05 Jan 2017
  • Loc: Decorah, IA, USA

Posted 25 September 2017 - 09:29 AM

More possible answers:

3. I believe that the purpose of the extender is for adding a camera.

4. The fan is to speed up the process of thermal equilibration of the primary mirror with the ambient temperature outside. If the temperature where you store the telescope is close to the outside temperature when you are observing, you might not need the fan. If, for example, your house is warm and it is cold outside, you can put the telescope outside and turn on the fan some time before you want to use it, and the mirror will cool off.

5. Open clusters are among the easiest DSOs to see because they can be made up of bright individual stars. Of course the world is Pleiades M45 are the largest and brightest example and if you stay up late or wait a month, they will be rising in the east. Other nice open clusters are the Perseus double cluster, the Alpha Persei association Mel 20, M52 in Cassiopeia.

8. The most obvious effect of the inverted view is that if you move the telescope one direction, then the view in the eyepiece moves in the opposite direction. I like to compare the view that I see in binoculars to what I see in the the eyepiece. You can find the same star in both, then practice moving the telescope a small amount and matching what you see in the telescope to what you see in the binoculars.

If you don't yet have a pair of binoculars and a basic planisphere (map of the constellations) then they are inexpensive and go very well alongside a new dobsonian telescope.

http://www.skymaps.com/downloads.html has a very simple one page monthly brochure that lists what you can see that month, including the easiest DSOs to see either naked eye or with binoculars or a telescope. To increase my chances of success, I like to use binoculars on objects listed as "naked eye" and use a telescope for objects listed for "binoculars".

#12 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 09:38 AM

1) 4 rays looking an "X"  are the diffraction spikes from the secondary mirror holder

 

2)it is likely bad seeing (e.g. the atmosphere is not steady, but there is a lot of turbulence, like boiling water in a pot)

 

3)to add those 35mm to the drawtube and attain the focus with certain equipment

 

4)to speed up the cooling of the primary mirror; ideally it should have the same temperature of the surrounding air. If there is a therml gradient between night and day, or between the storage site and observing site, it is indeed helpful; it may be useful also if the air temperature drops during the night

 

5)I suggest to download and install Stellarium or SkyChart (the former is easier to use, the latter is more powerful) and/or to purchase a small pocket atlas of the night sky; in any case,between Aquila and Sagittarius there are a lot of very bright and beautiful DSOs (the Lagoon nebula and Omega Centauri are among the brightest)

 

6)I use either distilled water and a droplet of detergent for dishes, or lens cleaner (those for LCDs or for photographical lenses); before I blow away the dust with a small dust blower (as those sold with camera cleaning kits), then dab the eyepiece with a cotton disk slightly damp, and blot the eyepiece with another dry disk. NEVER rub.

 

7)it is easier than you think: get a good star chart, choose a constellation and look at the faintest star you can see by the naked eye.

As a rule of thumb, if you can see the Milky way, the your sky is quite good

 

8) well, the inverted part relates to the horizon, but DSOs are not squared to our horizon...this is why nobody really cares about the fact that astronomical telescopes provide an inverted view (btw, some DSOs look "right" only with "inverted" telescopes, e.g. the notorious Swan Nebula is topside down in my refractor with an astronomical prism)

Thanks for all your help.

1) The spikes don't look like an "  X ".  The spikes are directed towards 1 quadrant only. Is it possible to remove them?
3) Do I need to use that with a Barlow?

4) The expected temperature various from 33`C (91 `F) to 25'C (78`F) do I need to worry about the cooling?
7) The thing is can't see the milky way in my area. frown.gif 
8) I was worried that I somehow tilted the primary mirror.



#13 rahulm

rahulm

    Lift Off

  • -----
  • topic starter
  • Posts: 19
  • Joined: 28 May 2017

Posted 25 September 2017 - 09:57 AM

More possible answers:

3. I believe that the purpose of the extender is for adding a camera.

4. The fan is to speed up the process of thermal equilibration of the primary mirror with the ambient temperature outside. If the temperature where you store the telescope is close to the outside temperature when you are observing, you might not need the fan. If, for example, your house is warm and it is cold outside, you can put the telescope outside and turn on the fan some time before you want to use it, and the mirror will cool off.

5. Open clusters are among the easiest DSOs to see because they can be made up of bright individual stars. Of course the world is Pleiades M45 are the largest and brightest example and if you stay up late or wait a month, they will be rising in the east. Other nice open clusters are the Perseus double cluster, the Alpha Persei association Mel 20, M52 in Cassiopeia.

8. The most obvious effect of the inverted view is that if you move the telescope one direction, then the view in the eyepiece moves in the opposite direction. I like to compare the view that I see in binoculars to what I see in the the eyepiece. You can find the same star in both, then practice moving the telescope a small amount and matching what you see in the telescope to what you see in the binoculars.

If you don't yet have a pair of binoculars and a basic planisphere (map of the constellations) then they are inexpensive and go very well alongside a new dobsonian telescope.

http://www.skymaps.com/downloads.html has a very simple one page monthly brochure that lists what you can see that month, including the easiest DSOs to see either naked eye or with binoculars or a telescope. To increase my chances of success, I like to use binoculars on objects listed as "naked eye" and use a telescope for objects listed for "binoculars".

Thanks

 

4) The expected temperature varies from 33`C (91 `F) to 25'C (78`F) do I need to worry about the cooling?
5) Simply forgot about the M45. Thanks for reminding about that one.
8) Currently, I don't have binoculars with me.  I was expecting a perfectly inverted view. But what I am getting is getting is an inverted image rotated 30 degrees.



#14 drneilmb

drneilmb

    Ranger 4

  • *****
  • Posts: 395
  • Joined: 05 Jan 2017
  • Loc: Decorah, IA, USA

Posted 25 September 2017 - 12:13 PM

Thanks

4) The expected temperature varies from 33`C (91 `F) to 25'C (78`F) do I need to worry about the cooling?


You don't need to worry about cooling simply because of warm temperatures. You only need to worry if you move the telescope from someplace warm to someplace cold (or vice versa). If your house is close to the outside temperature, then you may never need to use the fan.

5) Simply forgot about the M45. Thanks for reminding about that one.
8) Currently, I don't have binoculars with me. I was expecting a perfectly inverted view. But what I am getting is getting is an inverted image rotated 30 degrees.


I haven't ever paid careful attention to the angle of the image. My intuition is that it depends on the position of the focuser around the tube and that a 30 degree angle would be reasonable. With practice, I believe you will get very used to it.

#15 stargazer193857

stargazer193857

    Fly Me to the Moon

  • *****
  • Posts: 5102
  • Joined: 01 Dec 2013
  • Loc: Southern Idaho

Posted 25 September 2017 - 01:20 PM

Welcome to Cloudy Nights, the friendliest, most knowledgeable astronomy forum on the net. Also the biggest for that reason.

#16 wrnchhead

wrnchhead

    Mariner 2

  • -----
  • Posts: 238
  • Joined: 28 Aug 2017
  • Loc: NE Kansas

Posted 25 September 2017 - 07:35 PM

Rahulm, I am only a couple of days ahead of you with the same scope. I saw my first 2 DSOs last weekend from a darker site, and after learning what I was looking for, found them again from home. Judging your location compared to mine, my site is worse, so you should be able to find them. The Ring Nebula (M57) was my first, in Lyra. I star hopped to it and at first, didn't realize I was seeing it, I thought it was just an out of focus star. Then I realized I was actually seeing it. My second was the Andromeda galaxy (M31). Since I read that this is your first telescope, I think it helps to realize you are basically looking for fuzzy objects, not Hubble images. I am sure there are other DSOs you will be able to see, but as I am also fairly inexperienced, I am just sharing with you what I was able to find and believe you should be able to find (for starters)

 

I found your and my light pollution ratings at this site http://darksitefinde...aps/world.html 

 

The 35mm extender is to allow other some eyepieces to come into focus. With my 30mm eyepiece, I don't use the extender, but loosen the set screws in the focuser, and pull the eyepiece out just about 13mm, which allows it to focus. You may want to try the extender while trying to view Saturn. 

 

If your first shot is of your collimator, it looks to be properly collimated to me. At least, not too far out. i have recently read (on this site) that the best time to collimate is after your scope is adjusted to the temperature (at least fine tune it then, I don't believe your scope is too far out).

 

The fan is probably optional, but it speed the process of equalizing the temperature. 


  • Chris Johnson likes this

#17 beggarly

beggarly

    Ranger 4

  • -----
  • Posts: 372
  • Joined: 12 Jun 2015
  • Loc: Belgium

Posted 26 September 2017 - 12:43 AM

You can check sky conditions with: https://www.meteoblu...a_india_1259163




CNers have asked about a donation box for Cloudy Nights over the years, so here you go. Donation is not required by any means, so please enjoy your stay.







Cloudy Nights LLC
Cloudy Nights Sponsor: Astronomics