Setting Up a City Telescope in an Apartment or Condo

 

A large majority of amateur astronomers have nice large backyards with decent sky access for our telescopes.  But not all of us.

 

What if your only sky access is a balcony?  Even worse…., what if you don’t even have a balcony, only a window?

 

Many astronomers will find it quite difficult to believe that you can image reasonably well from a light-polluted suburban backyard or worse, from a high-rise balcony in the city center.  Below I’ll show you the setup of how to image from a city balcony.  And if you don’t have a balcony I’ll show you how to image through an open window in a light-polluted big city.  Yes, right through an open window.  I’ve done it for years.

 

Here’s how….

Balcony Telescope Setup

 

Whether apartment or condo your objective here is successful but discrete night-time astro-imaging from a city balcony.  Imaging from a balcony has many advantages the biggest of which is convenience, you simply don’t have to go very far to get to your “observing site”.

 

Let’s see how to do it…

 

  1. Test your balcony’s motion stability.  Do an imaging test by literally jumping up and down on the balcony, yes jump.  Does the telescope image move very much?  This way you’ll know how much balcony movement you can safely do while imaging at night.  I found my 9th-floor concrete balcony to be extremely stable.  I can walk around without any imaging concern.

  2. If the balcony wind-speed is anything more than “light” wait for another night.  Almost any wind is your enemy.

  3. Consider using a dew-shield as a “light-shield” to protect the telescope from any local direct lighting.  As your light-shield will hang out over the balcony make sure it is securely fastened!

  4. Balconies can be flooded by city light at night.  Depending on what hardware you have at the camera end of your telescope some of this light can easily leak into your images.  For example, my filter wheel leaks a lot of light onto the camera sensor.  To fix this I drape a light-weight black cloth over it.

  5. Turn off any apartment lighting that faces the balcony.  Not only will it keep your balcony darker but you don’t want to put on a silhouetted light-show of your nocturnal activities to your neighbors.

  6. Balcony Telescope Placement

    • Choose a balcony location.  One part of the balcony might have a slightly better view of the sky than the other and one end of it may have better shielding from local lighting.  Mine does on both counts.

    • Place the telescope as close to the balcony railing as you can without its movement striking the railing.  This gives you maximum sky exposure.  My AZ range is 145 degrees.

    • You probably have another balcony above you so try to position your telescope as low as is practical.  This will give your telescope the most sky elevation possible.  My maximum is 70 degrees EL.

    • What are your telescope’s EL and AZ observing limits?  This can be easily determined by reading out the angles from the telescope’s handset.  Record them.

    • Balconies are sloped about 1.5 degrees for water runoff.  Make sure your tripod or telescope platform is actually level.

  7. Depending on your software you may be able to program your balcony’s visibility limits into your telescope or even your night skies planning software.

  8. Use planetarium software.  I use the wonderful and free program Stellarium.  With it and your surveyed balcony limits above, you’ll know exactly what sky objects are visible from your balcony at any time of the year and on any date.

  9. Due to heavy light-pollution gradients choose a minimum EL for imaging.  I’ve chosen 30 degrees as my minimum.  Choose targets highest in the sky.  The highest elevation yields the least light pollution.

  10. You’ll need at least one table for your balcony things…, a laptop and your telescope accessories plus an outdoor storage container where you can leave some things 24/7.

  11. Depending on your situation you may be able to leave your telescope’s tripod permanently outside on the balcony and bring out only the telescope each time.  If so, you’ll need an all-weather cover for it.  Your cover can be as simple as two large extra-duty garbage bags one inside of the other.  Make sure these have a pull-string for closing them.  Commercial covers are also available.  This saves both apartment space and setup time.  For three years I left my complete but covered telescope outside in its balcony observing location.

  12. If others can see your balcony activities don’t display your telescope during the daytime.  For your own peace-of-mind, I advise the following simple balcony setup procedure…

    • At Dusk - setup your innocent looking items first.  These are items and activities that if others are watching, would not find suspicious.  That could be just about everything…, except bringing out your telescope.

    • When Dark - only then should you bring out your telescope.

  13. Avoid using lights on your balcony at night as this can also attract a neighbor’s suspicion.  That means flashlights, laptop screens, bright power-on indicators, etc.  I use a very low power flashlight that never points out from the balcony, masking tape over power-on indicators to lower their brightness and a night-mode laptop screen running at low brightness and that faces away from the railing.

  14. Keep your nocturnal activities extra quiet.  Strange and constant noises are not what your immediate neighbors want to hear at night.  I lower the telescope’s slew speed to greatly reduce motor noise.  If any of your equipment beeps in operation either reduce it to a minimum volume or turn it off completely.  Be quiet and avoid that knock on your door.

  15. If you don’t already have it, install a power plug on your balcony.  This can be as simple as running an extension cord from inside.

  16. If there is a temperature difference between outside and inside your apartment or condo keep the balcony door closed.  At times my biggest source of bad seeing was warm apartment air flowing out to the telescope through the open balcony door.  It really can make a difference.

 

 

Open Window Telescope Setup

 

Firstly, never bother trying to use a telescope through a closed window.  Unless the window is of optical quality glass and none are, it will not work.

 

If you don’t have a balcony or it faces the wrong direction, what can work is imaging through an open window.  I’ve done it successfully many times even of planets that require very long focal lengths.  Working from your dining room table is also a very comfortable way to image the night-time skies.

 

Atmospheric "Seeing"

Imaging through an open window will mix the different temperatures of indoor and outdoor air at the end of your telescope.  If you live in a climate with seasons you may not be able to use your telescope through an open window in the winter as there can be too much of a temperature difference.  This mixing can create very bad localized “seeing”.  If you want to image planets you'll need very good seeing, if deep-sky generally you don't need it.

 

You Do Have Some Control Over Your Local Seeing...

 

  1. Select nights where the outdoor and indoor air temperatures are the same or similar.  The less the temperature difference the less your localized bad seeing will be.

  2. To reduce potential mixing, position the end of the telescope as far out the window as is practical and safe.  Even better, use a dew shield at the end of the telescope to extend this distance.  The more the extension the less the mixing.  Make sure your dew shield is securely attached!

  3. To reduce mixing further you still have a few more options…

    • Reduce the open window area to a minimum by blocking any unused window sections.  I use an inexpensive light-weight piece of foam-board fitted into the window.

    • Test the window’s air-flow direction.  Is it flowing in or out of the window?  An out-direction will cause mixing at the telescope end while an in-direction does not.  If the flow is outward which causes mixing, try experimenting with other doors and windows in your apartment or condo by opening and closing them.  The idea here is to change your telescope window’s flow direction or its speed to your telescope’s advantage.

  4. Use a window and telescope position so that the telescope can freely move around the open window.  If the telescope strikes any part of the window frame you’ll lose your alignment.  You may even be able to program the telescope to operate only in a certain sky area so as to avoid striking the window frame.

  5. Drape a light-weight black cloth over the camera end of the telescope to keep out stray room light.  For me it makes a big difference.

  6. As you can’t do a full telescope alignment through a window use the “One Star” or “Solar System” alignment option.  As your window viewing will be limited to a small part of the sky around that single alignment object your go-to accuracy can be surprisingly good.

Balcony setup using a custom made fold-down platform.  Telescope attaches with just three hand-tightened bolts.

Window setup.  Notice the custom-fitted black foam-board in the window's open top.

Same window setup but with a custom curtain to reduce the wind flow at the window's open bottom.

The White Zone

An Urban Astronomer's Light Pollution Guide to Balcony Imaging

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